Iec 60556 2016

The vibratin coi method [1] [2] has the ad antages of e sier sample mou tin an simpler mec anical ar an ement when me s rements over a ran e of temp ratures are req ired, p rtic larly at

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IEC 60556

Editio 2.1 2 16-0

CONTENTS

FOREWORD 6

1 Sco e 8

2 Normative referen es 8

3 Terms an definition 8

4 Saturation mag etization M s 8

4.1 General 8

4 2 Object 9

4.3 The ry 9

4.4 Test sample 10 4.5 Me s rin a p ratu for the vibratin coi method (VCM) 10 5 5 Me s rin a p ratu 2

5.4 Test sp cimen 21

4.7 Cal bration 16 4.8 Me s rin proced re 17 4.9 Calc lation 18 4.10 Ac urac 18 4.1 Data presentation 19 5 Mag etization (at sp cified field stren th) M H 19 5.1 General 19 5.2 Object 19 5.3 The ry 19 4.6 Me s rin a p ratu for the vibratin sample method (VSM) 13 5.6 Cal bration 2

5.7 Me s rin proced re 2

5.8 Calc lation 2

5.9 Ac urac 2

5.1 0 Data presentation 2

6 Gyromag etic resonan e l newidth ∆H an efective L n é factor g ef (general) 2

6.1 General 2

6.2 Object 2

6.3 The ry 2

6.4 Test sp cimen an cavities 2

6.5 Me s rin a p ratu 3

6.6 Me s rin proced re 3

6.7 Calc lation 3

6.8 Ac urac 3

6.9 Data presentation 3

7 Gyromag etic resonan e l newidth ∆H 10 an efective L n é factor g 10 (at 10 GHz) 3

7.1 General 3

7.2 Object 3

7.3 The ry 3

7.4 Test sp cimen an cavity 3

7.5 Me s rin a p ratu 3

7.6 Me s rin proced re 3

7.7 Calc lation 3

IEC 6 5 6:2 0 +AMD1:2 16 CSV – 3 –

 IEC 2 16

7.8 Ac urac 3

7.9 Data presentation 3

8 Spin-wave resonan e lnewidth ∆H k 3

8.1 General 3

8.2 Object 3

8.3 The ry 3

8.4 Test sp cimen an cavity 3

8.5 Me s rin a p ratu 4

8.6 Cal bration 4

8.7 Me s rin proced re 4

8.8 Calc lation 41

8.9 Ac urac 41

8.10 Data presentation 41

9 Efective l newidth ∆H ef 41

9.1 General 41

9.2 Object 41

9.3 The ry 4

9.4 Test sp cimen an cavity 4

9.5 Me s rin a p ratu 4

9.6 Cal bration 4

9.7 Ap aratu adju tment 4

9.8 Me s rin proced re 4

9.9 Calc lation 4

9.10 Ac urac 4

9.1 Data presentation 4

10 Complex p rmitivity e r 4

10.1 General 4

10.2 Object 4

10.3 The ry 4

10.4 Test sp cimen an cavity 51

10.5 Me s rin a p ratu 51

10.6 Me s rement proced re 5

10.7 Calc lation 5

10.8 Ac urac 5

10.9 Data presentation 5

1 Ap arent den ity ρ p 5

1 1 General 5

1 2 Ap arent den ity (by men uration) 5

1 3 Ap arent den ity (by water den itometry) 5

12 Gyromag etic resonan e l newidth ΔH an efective g romag etic ratio γ ef by non resonant method 5

12.1 General 5

12.2 Object 5

12.3 Me s rin method 5

An ex A (informative) Method to calc late the l newidth u in a spre d he t sofware program 7

Bibl ogra h 7

Fig re 1 – Vibratin coi method – Sample an cois ar an ement 10

Fig re 2 – Mag etic field config ration 1

Fig re 3 – Me s rin a p ratu (VCM) 13

Fig re 4 – Vibratin sample method – Sample an coi ar an ement 14

Fig re 5 – Me s rin a p ratu (VSM) 15

Fig re 6 – Hy teresis c rves for a mag etic material: B(H ) c rve, M(H ) c rve 2

Fig re 7 – Test sample with comp n ation u it 21

Fig re 8 – Test sp cimen 2

Fig re 9 – Me s rin circ it for determinin mag etization (at sp cified

field stren th) M

H 2

Fig re 10 – Mi er integrator 2

Fig re 1 – Cavity for me s rement of g romag etic resonan e l newidth an

ef ective L n é factor 2

Fig re 12 – Stripl ne resonator for me s rement of g romag etic resonan e l newidth

an efective L n é factor at low freq en y 2

Fig re 13 – Sc ematic diagram of the eq ipment req ired for me s rement of

g romag etic resonan e lnewidth an ef ective L n é factor 31

Fig re 14 – Sc ematic diagram of the eq ipment req ired for me s rement of

g romag etic resonan e lnewidth an ef ective L n é factor at 10 GHz 3

Fig re 15 – Subsidiary a sorption an saturation of the normal resonan e 3

Fig re 16 – Pulse deterioration at on et of s bsidiary resonan e 3

Fig re 17 – Me s red critical r.f field stren th as a fu ction of pulse d ration t

d 3

Fig re 18 – Typical TE

10cavity for the me s rement of spin-wave resonan e

l newidth at a out 9,3 GHz 3

Fig re 19 – Bloc diagram of spin-wave resonan e l newidth test eq ipment 4

Fig re 2 – Sectional view of the cavity with sp cimen 4

Fig re 21 – Dimen ion of a cavity desig ed for resonan e at a freq en y of 9,1 GHz 4

Fig re 2 – Sc ematic diagram of eq ipment for me s rin ef ective l newidth ΔH

ef 4

Fig re 2 – Determination of Q

0 4

Fig re 2 – Ide l resonant cavity with sp cimen, u ed for the retical calc lation

(sectional view) 4

Fig re 2 – Dimen ion of the resonant cavity with sp cimen 51

Fig re 2 – Sc ematic diagram of eq ipment req ired for the me s rement of

complex dielectric con tant 5

Fig re 2 – Sc ematic drawin of s ort circ ited microstrip l ne fixture with sp cimen 5

Fig re 2 – Eq ivalent circ its of s ort circ ited microstrip l ne 5

Fig re 2 – Cros -sectional drawin of al-s ielded s orted microstrip l ne with

sp cimen 5

Fig re 3 – Bloc diagram of me s rement s stem 6

Fig re 31 –Observed a sorption c rve of imaginary p rt ημ”L of in u tan e for a

5 mm s uare garnet sp cimen with 0,2 2 mm thic nes an Ms = 0,0 T 6

Fig re 3 – As umed eq ivalent circ it of the test fixture 6

Fig re 3 – Stru ture of test fixture to me s re resonan e l newidth by tran mis ion 6

Fig re 3 – Model to me s re resonan e l newidth by tran mis ion 6

Fig re 3 – Test fixture for me s rement of resonan e l newidth by tran mis ion 6

Fig re 3 – Example of a test fixture ( oleran e: Clas f 6

IEC 6 5 6:2 0 +AMD1:2 16 CSV – 5 –

© IEC 2 16

Fig re 3 – Bloc diagram of the eq ipment for me s rin the resonan e l newidth 6

Fig re 3 – Me s rement proced res 6

Fig re 3 – Ste s to o tain resonan e l newidth by n merical analy is 71

Ta le 1 – Typical dimen ion of test fixture 5

Ta le 2 – Sp cimen s a e an typical dimen ion 5

Ta le 3 – The fixture con tants for 5 mm lon sp cimen 6

Ta le A.1 – Example of the lnewidth calc lation u in a spre d he t sof ware program 7

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In this Redl ne version, a vertical l ne in the margin s ows where the tech ical content

is modified by amendment 1 Addition are in gre n text, deletions are in strik through

IEC 6 5 6:2 0 +AMD1:2 16 CSV – 7 –

 IEC 2 16

International Stan ard IEC 6 5 6 has b en pre ared by IEC tec nical commite 51:

Mag etic comp nents an fer ite materials

This secon edition is a con oldation of the first edition an its amen ments 1 an 2

It in lu es editorial improvements as wel as improvements to the fig res

This stan ard is to b re d in conju ction with IEC 6 3 2

The Fren h version of this stan ard has not b en voted up n

This publ cation has b en drafed in ac ordan e with the ISO/IEC Directives, Part 2

The commit e has decided that the contents of the b se publ cation an its amen ment wi

remain u c an ed u ti the sta i ty date in icated on the IEC we site u der

"ht p:/ we store.iec.c " in the data related to the sp cific publcation At this date, the

GYROMAGNETIC MATERIALS

INTENDED FOR APPLICATION AT MICROWAVE FREQUENCIES –

1 Scope

This International Stan ard des rib s method of me s rin the pro erties u ed to sp cify

p ly ry tal ne microwave fer ites in ac ordan e with IEC 6 3 2 an for general u e in fer ite

tec nolog These me s rin method are inten ed for the in estigation of materials,

general y refer ed to as fer ites, for a pl cation at microwave freq en ies

Sin le cry tals an thin fi ms generaly fal outside the s o e of this stan ard

NOT 1 For th p rp ses of this sta d rd, th words “ferite” a d “microwa e” are use in a bro d se se:

– b “ferites” is me nt n t o ly ma n to-diele tric c emic l c mp n nts h vin a spin l crystal stru ture, b t

also materials with g rn t a d h x g n l stru tures;

– th “microwa e” re io is ta e to in lu e wa ele gths a pro imately b twe n 1 m a d 1 mm, th maininterest

b in c n e trate o th re io 0,3 m to 10 mm

NOT 2 Ex mples of c mp n nts emplo in microwa e ferites are n n-re ipro al d vic s su h as circ lators,

isolators a d n n-re ipro al p ase-shifers Th se c nstitute th major field of a plc tio , b t th materials ma

b use in re ipro al d vic s as wel for e ample, mo ulators a d (re ipro al) p ase-shifers Oth r a plc tio s

in lu e g roma n tic fiters, lmiters a d more so histic te d vic s, su h as p rametric amplfiers

2 Normative references

The folowin referen ed doc ments are in isp n a le for the a pl cation of this doc ment

For dated referen es, only the edition cited a pl es For u dated referen es, the latest edition

of the referen ed doc ment (in lu in an amen ment a pl es

IEC 6 0 0-2 1, In te rn ton al Ele ctrote ch n icalVo cab ula ry (IEV) – Part 2 1: Ma ne tic m ate rials

comp one nts

IEC 6 2 5:2 0 , Calcu lato of th efectv p aramete rs ofma n tc p ie ce p arts

IEC 6 3 2:19 2, G uide for th draftn ofsp cificato s for microwa e ferie s

Saturation mag etization is a c aracteristic p rameter of fer ite materials It is widely u ed in

the retical calc lation , for in tan e in computation of ten or p rme bi ty comp nents (se

IEC 6 0 0-2 1) In a variety of microwave a pl cation , saturation mag etization determines

the lower freq en y lmit of the device, mainly d e to the oc ur en e of so-cal ed low- ield

los when the material is u saturated

IEC 6 5 6:2 0 +AMD1:2 16 CSV – 9 –

 IEC 2 16

4.2 Object

The o ject is to give two simi ar tec niq es for me s rin saturation mag etization These

are the vibratin coi method (VCM) an vibratin sample method (VSM)

The vibratin coi method [1] [2] has the ad antages of e sier sample mou tin an simpler

mec anical ar an ement when me s rements over a ran e of temp ratures are req ired,

p rtic larly at low temp ratures

The vibratin sample method is more ac urate, given a simi ar degre of ela oration in

electronic a p ratu

The eq ipment ne ded in b th cases is very simiar an the cal bration method are identical

The same test samples can b u ed for either tec niq e

4.3 The ry

When a sphere of isotro ic mag etic material is placed in a u iform mag etic field, the sphere

b comes u iformly mag etized in the direction p ral el to the a pl ed field The sphere now

prod ces its own external mag etic field, eq ivalent to that of a mag etic dip le at the centre

of the sphere an orientated p ral el to the direction of mag etization

If a smal detection coi (in practice a p ir wou d in o p sition) is now vibrated at smal

ampl tu e, close to the sample sphere an in a direction at right an les to the a pl ed field, a

dxd

Ne

s

may b fou d by comp rison:

s

ss

VV

ee

MM

c

cc

33

c

cc

ss

s

dd

EE

Identical eq ation a ply in the VSM case, when the sample is vibrated whie the coi remain

stationary

4.4 Test sample

For the dip le as umption to b val d, the test sample s al b a sphere, whose deviation from

rou d es is not more than 0,5 % The p rcentage deviation from rou d es is defined as

(5)

For most fer ite materials, a diameter of a out 2,5 mm is s ita le If it is les than 1 mm, a

re sona le sig al- o-noise ratio wi b dif ic lt to ac ieve, p rtic larly when M

s

is low

Spheres larger than a out 4 mm are les con enient to ma e an it is not so e s to maintain

a u iform a pl ed field over the volume of the sphere

It may b p rmis ible to u e other than spherical samples, provided that the in u ed voltage

can b s own to b a l ne r fu ction of the mag etization to within the ac urac req ired, an

that the cal bration sample has identical dimen ion to the samples to b me s red

4.5 Me s rin a p ratus for the vibrating coi method (VCM)

4.5.1 Ar angement of detection coi s and sample

A s hematic diagram of the ar an ement of the detection coi s an the sample is s own in

Fig re 1 Fig re 2 in icates the direction of the a pled an sample field

The sample is rigidly mou ted b twe n the p le-pieces of an electromag et, in s c a way

that its p sition relative to the detection coi s is re rod cible to ± ,1 mm in an direction Al

p rts of the sample holder s al b made of non-mag etic material

The detection cois are an identical p ir wou d in series o p sition They are atac ed to the

vibrator by a rigid, non-mag etic arm an are located as close to the sample as practica le

Their axes are normal y p ral el to the direction of vibration, but other config ration are

The direction of vibration ( he x-direction) is at 9 ° to the z-axis of the electromag et

(Fig re 1), i.e p rp n ic lar to the mag etostatic field direction, an the ampl tu e s al b of

the order of 0,0 mm to 0,5 mm The freq en y is not critical, but would normal y b b twe n

2 Hz an 2 0 Hz, althou h freq en ies outside that ran e are ac e ta le Motion of the coi s

in the z- an y-direction s al b l mited by me n of s ita le mou tin to not more than 1 %

of that in the x-direction Some me n of sta i zin the vibration ampltu e by u e of a

fe db ck lo p may b in orp rated if req ired

4.5.2 The electromagnet

The mag etostatic field s al b ca a le of ful y saturatin a spherical sp cimen of the

material to b me s red For most microwave fer ites, a field of 3 0 kAm

Sin e the u iformity of the field is de en ent on the field-stren th, me s rements s al

alway b made at the a pl ed field at whic cal bration an zero-set in (se 4.8) have b en

car ied out

4.5.3 El mination of a pl ed field ef ects

If the a pled field were whol y u iform an had no radial comp nents, whi e the direction of

vibration was exactly at rig t an les to the a pl ed field, the the ry of 4.3 could b a pl ed

directly to the exp rimental ar an ement of Fig re 1

However, as in icated in Fig re 2, the a pled field is not u iform, an its direction an

mag itu e vary from p int to p int More ver, it is impractica le to ma e an identical p ir of

detection coi s The an le of vibration wi deviate from 9 ° an some resid al motion in the

y-an z-direction wi alway b present

Voltages wi therefore b in u ed in the cois by the in omogeneity of the a pl ed field The

ten to can el out where s those d e to the sample dip le field wi ad up

However, complete can elation can ot in general b ac ieved with one p ir of coi s alone

Therefore, a secon p ir of cois, the comp n atin coi s, is u ed These are mou ted on the

same formers as the sample cois, but are wou d in series, so that the voltages in u ed by H

z

are ad itive A comp n atin voltage can then b o tained, whic may b adju ted in

ampl tu e an phase to b lan e out the voltage in u ed in the sample coi s by H

z

The efect of H

x

is more dif ic lt to el minate b cau e the voltages in u ed in the sample cois

wi b ad ed in the same way as those d e to the dip le field However, in general, the

variation of H

x

with x wi b diferent from that of the sample dip le field The two sig als wi

therefore difer in phase an may b distin uis ed by me n of a phase sen itive detector

4.5.4 Electronic instrumentation

A s hematic diagram of the me s rin a p ratu is s own in Fig re 3 The vibrator is driven

by a low- req en y os i ator (9), whic may be tu a le, an a p wer ampl fier The ampl tu e

of the os i ator output an the gain of the p wer ampl fier s al b s ficiently sta le to

provide a con tant drive to the vibrator to within ± ,3 %, afer warm-up If this is not p s ible,

some me n of sta i zin the vibration ampl tu e s al b provided The os i ator freq en y

s al b sta le to 0,0 % af er warm-up

The output from the comp n atin coi s (1(c) is b lan ed again t that of the sample cois

(1(s) by me n of the diferen e ampl fier (4), u in the varia le at en ator (2) an phase

s if er (3) The phase s if er s al b ful y varia le over 3 0° an its resolution s al b at

le st ± ,1° Neither the phase s ifer nor the at en ator ne d to b cal brated

The dif eren e amplfier s al have a low enou h noise level at low freq en ies to al ow

precise zero setin The exact req irements wi de en on the desig of the cois an other

eq ipment A varia le gain control may b in orp rated

The low-p s fi ter (5) s al red ce al harmonic by at le st 2 dB with resp ct to the

fu damental freq en y

The selective ampl fier, whic is tu ed to the os i ator freq en y, s al have a b n width of

the order of 1 % an s al b tu a le if the os i ator is not tu a le

The phase-sen itive detector (7) s al have a resolution b t er than 3° an either the

referen e or sig al c an el s al b varia le over 3 0° in phase The phase set in s al b

in e en ent of the ampl tu e of the input to either c an el

The meter (8) may b an analog e or digital typ When me s rements are to b made over a

ran e of temp ratures, an X–Y-recorder may b s bstituted for the meter, one axis to record

a l ne r fu ction of mag etization, the other a l ne r fu ction of temp rature Both axes s al

b calbrated to the ac urac req ired The temp rature me s rin device, normaly a

thermocouple, s al b in close thermal contact with the sample itself

Al the electronic in truments s al have adeq ate temp rature sta i ty to en ure the req ired

ac urac over the ran e of ambient temp ratures to b met in u e

In the vibratin sample case, the detection coi s (Fig re 4) are rigidly mou ted b twe n the

p le-pieces of the electromag et, but in s c a way that freq ent smal adju tments are

p s ible Normal y, their axes are at rig t an les to the a pl ed field an p ral el to the

direction of vibration, but other config ration [5] are ac e ta le The me n sample p sition

is on the axis of the electromag et, normal y located s mmetrical y with resp ct to the

detection coi s Its p sition s al b re rod cible to ± ,1 mm It is rigidly mou ted on a non

-mag etic vibratin arm, at ac ed to a vibrator, an is as close to the detection coi s as

practica le

The direction of vibration ( he x-direction) is at 9 ° to the z-axis of the electromag et

(Fig re 4), i.e p rp n ic lar to the mag etostatic field direction, an the ampl tu e s al b of

the order of 0,0 mm to 0,5 mm The freq en y is not critical, but would normal y b b twe n

2 Hz an 2 0 Hz, althou h freq en ies outside that ran e are ac e ta le Motion of the

sample in the z- an y-direction s al b l mited by me n of a s ita le mou tin to not more

than 1 % of that in the x-direction Some me n of sta i zin the vibration ampl tu e by u e of

a fe db ck lo p may b in orp rated if neces ary

A smal p rmanent mag et is at ac ed to the vibratin arm, far enou h away from the

electromag et to b u afected by it Two smal cois are mou ted rigidly on either side of this

mag et to detect its field A smal coi car yin a precisely controled direct c r ent may b

No precaution ne d b ta en to cou teract c rvature an non-u iformity of a pl ed field,

provided that a u iformity of a out 3 % over the volume of the sample is maintained A radial

field of up to 1 % of the lon itu inal field is p rmis ible

The mag etostatic field s al b ca a le of ful y saturatin a spherical sp cimen of the

material to b me s red For most microwave fer ites, a field of 3 0 kAm

A s hematic diagram of the electronic in trumentation is s own in Fig re 5 The simplest

ar an ement u es only items 1 to 8, an alows p int by-p int me s rements to b made at

fixed temp ratures The calbrated p tential divider (3) is u ed to b lan e the voltage in u ed

in the b lan in cois again t that in the sample coi s The n l p int is o served by me n of

the os i os o e (5) Mag etization is calc lated from the p tential divider setin

Alternatively, the n l b lan e may b made with the empty sample holder in p sition The

out of b lan e sig al on in ertion of a sample is then pro ortional to mag etization This

sig al may b re d directly from the meter (5) or os i os o e For contin ou plotin of M

s

as a fu ction of temp rature, an X–Y-recorder may b s bstituted for the os i os o e

Gre ter sen itivity an b t er sta i ty may b o tained by u e of a phase sen itive detector (9)

to detect the sig al, whic may then b o served by me n of a meter or recorder

If a d.c coi (12) is u ed in te d of a p rmanent mag et to o tain the b lan in voltage,

automatic n l b lan in may b ac ieved by fe din the output of this phase sen itive

detector to the d.c coi The c r ent in the coi is then directly pro ortional to mag etization

The coi c r ent may b me s red by me n of a d.c ammeter in series with it, or by a hig

-resistan e voltmeter in p ralel with the coi In the secon case, variation in coi resistan e

d e to temp rature c an es s al b comp tible with the degre of ac urac req ired in M

s

The vibrator is driven by a low- req en y os i ator, whic may b tu a le, an a p wer

ampl fier The ampl tu e of the os i ator output an the gain of the p wer ampl fier s al b

s f iciently sta le to maintain the drive to the vibrator at a con tant level, to within 0,3 % afer

warm-up If this is not p s ible, some me n of sta i zin the vibration ampl tu e s al b

provided The os i ator freq en y s al b sta le to within 0,0 % afer warm-up

The p tential divider s al b contin ou ly varia le with a resolution of 0,01 % or b ter an

s al b calbrated to the ac urac req ired

The dif eren e ampl fier s al have a s f iciently low noise level an s al in orp rate, or b

fol owed by, a selective ampl fier with a b n width of the order of 3 %, tu ed to the os i ator

freq en y The selective stage s al b tu a le if the os i ator is not tu a le

The req irements for the phase-sen itive detector are not strin ent A resolution of 10° is

adeq ate The phase setin s al b in e en ent of the ampl tu e of the input to either

c an el

The meters may b analog e or digital typ s When me s rements are to b made over a

ran e of temp ratures, an X–Y-recorder may b s bstituted for the meter, one axis to b a

l ne r fu ction of mag etization, the other a l ne r fu ction of temp rature Both s al b

cal brated to the ac urac req ired The temp rature me s rin device, normaly a

thermocouple, s al b in close thermal contact with the sample itself

Al the electronic eq ipment s al have adeq ate temp rature sta i ty to maintain the

req ired ac urac over the ran e of ambient temp ratures general y en ou tered in u e

4.7 Cal bration

4.7.1 Comp rison method

This method, whic is eq al y a pl ca le to either the vibratin coi or the vibratin sample

method , cal s for a stan ard sample whose saturation mag etization is ac urately known

The most u ual material for the stan ard is pure nick l, but other materials may b u ed if

their saturation mag etization is known ac urately enou h

The cal bration sample s al b a sphere (if the samples to b me s red are spheres) an b

of a simi ar order of size (If samples other than spheres have to b me s red, calbration

samples with identical dimen ion s al b u ed.) The cal bration sphere s al s ow a

deviation from rou d es of not more than 0,5 % an its me n diameter s al b known to

within 0,1 % Stan ard metal c spheres s al b ful y an e led b fore u e

The den ity of the material to b u ed as a stan ard s al first b determined The generaly

ac e ted value for the saturation mag etization of 9 ,9 5 % pure nick l with a den ity of

den ity6

(kAm–1

(6)

However, the actual value for a sp cific sample may dif er from this by as mu h as 1 % [3],

de en in on purity, state of strain, a pl ed field, or ambient temp rature The ac urac of

the comp rison method is therefore l mited

4.7.2 “Slope” method

This method, whic is eq al y a pl ca le to either the vibratin coi or the vibratin sample

method , is b sed on the o servation that the voltage in u ed in the detection coi s by a

spherical sp cimen is directly pro ortional to the a pl ed field over the lower region of the

mag etization c rve [4] Furthermore, the con tant of pro ortional ty is in e en ent of the

p rme bi ty, provided that the later is s f iciently hig

Ac ordin to 4.3, the voltmeter re din E

x, for an sample x, can b writen:

3

XXX

dkM

1 H

x0i

NMH

is the relative p rme bi ty of the sample;

N is the demag etization factor whic is eq al to one- hird for a p rfect sphere

X

1/1

d

NH

kE

x

3

XX

is s f iciently hig , for example 2 0 0, the first term in the denominator can b neglected

in comp rison with N, an the p rameter k can be expres ed as

3

X

0x/

d

HE

A deviation from rou d es of 0,2 % le d to a maximum er or in N of 0,2 % [3]

The value of k th s o tained, u in a hig -p rme bi ty cal bration sample, can b in erted

into eq ation (7) whic is s bseq ently a pl ed to the u known sample, at saturation The

saturation mag etization of the u known sample M

s

Ed

E

kdE

is the voltmeter re din for the saturated u known sample, an

s bs ripts c an u refer to the cal bration sample an u known sample, resp ctively

This method do s not req ire an a solute cal bration stan ard

4.8 Me s rin proced re

4.8.1 Zero set ing – Vibrating coi method

The electromag et c r ent is switc ed on, with the empty sample holder b twe n the p les

The detection coi s are al owed to vibrate The at en ator an phase s if er are adju ted to

o tain a minimum output from the selective ampl fier, as o served on the os i os o e

The a pl ed field is then altered an the aten ator an phase s ifer setin s c eck d If

these have c an ed sig ificantly, the location of the cois is adju ted an the zero re-set, u ti

a p sition is fou d at whic the zero setin is s f iciently in e en ent of a pled field over

the ran e of interest

A calbration sample is placed in the holder an the phase sen itive detector adju ted u ti a

maximum re din is o tained on the voltmeter

4.8.2 Zero set ing – Vibrating sample method

The b lan in coi s are first made as in en itive as p s ible to the exact p sition of the

referen e mag et (or d.c coi ) In the a sen e of an sig al from the detection coi s, the

b lan in coi s are rotated a out the x-axis for maximum output They are then adju ted in

the z-direction for minimum output, in the y-direction for maximum output an the x-direction

for a maximum (if the coi s are s ort or minimum (if they are lon ) The output is now

in e en ent of smal c an es in the p sition of the mag et

The b lan in cois are then firmly fixed in p sition an the a ove adju tments are not

normal y re e ted

A sample is placed in the holder an simi ar adju tments car ied out for the sample coi in the

a sen e of a sig al from the b lan in coi s

4.8.3 Me s rement

Al the electronic eq ipment s al b switc ed on at le st 3 min b fore startin

me s rements, to al ow it to sta i ze at the ambient temp rature The zero re din is

c eck d with the sample holder empty an the a p ratu adju ted if neces ary

A cal bration sample is placed in the holder an the re din c eck d to en ure that it is

cor ect for that p rtic lar sp cimen at the ambient temp rature

The diameter of the spherical sample is me s red ma in at le st five se arate micrometer or

micros o e me s rements The deviation from rou d es is calc lated ac ordin to Eq ation

(5)

The sample is fixed in the holder an the a pl ed field set to the req ired value

In the VSM case, the p tential divider set in is adju ted to o tain a n l re din on the

os i os o e or, alternatively, if the n l has b en o tained for the empty sample holder, the

meter re din is noted If automatic n l b lan in with a d.c coi is b in u ed, the coi

c r ent is o served

In the VCM case, the meter re din is noted

The temp rature of the sample is also o served If me s rements are to b made over a

ran e of temp ratures, the temp rature is set to the lowest value to b u ed, al owin enou h

time for the en ironmental c amb r to sta i ze, an then in re sed at not more than 3 °C/min

u ti the whole temp rature ran e of interest has b en covered

4.9 Calc lation

The re din s are con erted into values of mag etization, u in either Eq ation (4) or (14)

ac ordin to whether the cal bration method was as des rib d in 4.7.1 or 4.7.2

4.10 Ac urac

The ac urac of either VCM or VSM de en s on the method of calbration If the comp rison

method is u ed, a s stematic er or of up to 1 % may b introd ced b cau e of u certainty in

the mag etization of the cal bration sample The slo e method is somewhat b ter b cau e

IEC 6 5 6:2 0 +AMD1:2 16 CSV – 19 –

 IEC 2 16

The relative er or for the VCM is typical y ± %

The relative er or for the VSM is typical y ±1,5 %

The relative er ors de en on the value of M

s, b in gre ter for low values of saturation

mag etization

4.1 Data presentation

Values of M

s

o tained by either method s al b q oted as fol ows:

saturation mag etization at a temp rature of θ °C: M kAm

–1

± estimated er or, where the

n mb r M is given to thre sig ificant fig res

If M

s

has b en ploted as a fu ction of temp rature, the actual c rve s al b given together

with an estimate of the ac urac of b th M

For the retical computation of ten or p rme bi ty comp nents, knowled e of the saturation

mag etization of the material is neces ary (se IEC 6 0 0-2 1) However, in general, the

fer ite material in a microwave comp nent is not completely saturated

For example, in the recently develo ed so-caled latc in devices, the fer ite is in a state of

remanen e Therefore, a method has b en sou ht where y more general information on the

h steresis lo p pro erties of a material can b o tained The a pl ca i ty of this method is

somewhat l mited by the fact that the test sp cimen has to b a toroid, or at le st a closed

mag etic circ it that can, with s f icient ac urac , b expres ed in terms of an eq ivalent

toroid

5.2 Object

The me s rin method to b des rib d has b en develo ed primari y in order to me s re

mag etization However, it also p rmits simultane u me s rement of a n mb r of other

mag etic pro erties, for in tan e remanent mag etization an co rcivity when the material is

in a c clc mag etic con ition The “s uarenes ratio”, M

rM

H, of the material may b

calc lated, an the h steresis lo p can b contin ou ly displayed on an os i os o e d rin

me s rements The lat er fact ena les the sen itivity of the material to mec anical stres to

b c eck d q al tatively

By placin the test sp cimen in a programmed temp rature test c amb r al q antities can b

o tained as fu ction of temp rature By al owin for a s f icient temp rature swe p ran e,

the Curie temp rature an , for certain materials, the comp n ation temp rature may b

If the ratio of outer to in er diameter of the toroid is close to u ity, al the field q antities can

b as umed to b re sona ly con tant over the toroid cros -section

If H is varied p riodical y an s mmetrical y an B is me s red simultane u ly an ploted as

a fu ction of H in a Cartesian co-ordinate s stem, a d namic B(H ) lo p is o tained (Fig re 6 )

This c rve can b c an ed into an M(H ) lo p by s btractin from B a q antity eq al to µ

0

H

an dividin by µ

0(Fig re 6 ) If the variation in H is s ficiently large, the heig t of the c rve

b comes in e en ent of an further in re se in H an eq al to M

s In this case, the interce ts

of the lo p with the H -axis cor esp n to the c cl c co rcivity

cJH

turn is u iformly distributed over a toroidal core havin

rectan ular cros -section, a c r ent I throu h that win in gives rise to a mag etic field in ide

the core with a me n value eq al to

m1

2 r

IN

12

m

/1/1

/

ln

rr

rr

turn is u iformly distributed over the same core, an

electromotive force E, pro ortional to the time derivative of the flu den ity in the core is

in u ed in that win in :

tB

kE

dd

IEC 6 5 6:2 0 +AMD1:2 16 CSV – 21 –

 IEC 2 16

Had the same two win in s b en placed on a non-mag etic core, the in u ed voltage would

have b en pro ortional to the time derivative of the field stren th:

tH

kE

dd

0'

µ

−

The ar an ements des rib d a ove cor esp n to a fer ite-core an an air-core tran former,

resp ctively If two s c tran formers, one of either kin , are con ected in series o p sition,

as s own in Fig re 7, the total output voltage U is eq al to

tB

kEEU

dd

dd

0µ'

(2 )

when e

tM

kU

dd

0µ

−

By integratin the voltage U, a voltage- ime integral pro ortional to M can b o tained Th s,

sin e H is pro ortional to I, there are two electrical q antities that may b u ed to give an

A toroid is made from the material to b in estigated An example of s ita le dimen ion for

the toroid is given in Fig re 8 The dimen ion may b sl g tly c an ed, but the ratio of in er

to outer diameter s al alway ex e d 0,7

A minor p rtion of one of the flat sides of the sp cimen is si ver-co ted A s ita le si ver

pre aration s ould s ow go d ad esion an soldera i ty afer c rin

A hig meltin -p int solder (meltin -p int a proximately 310 °C) is pre ared by ma in an

al oy of a out 9 % by weig t of le d an the remain er tin This al oy, whic can b u ed in

the same way as ordinary solder, is u ed to fix a thermocouple (co p r-con tantan) to the

siver-co ted p rtion of the core s rface This thermocouple me s res the re l core

temp rature with s f icient ac urac Some sort of protective co tin may b a pl ed to the

thermocouple ju ction to minimize direct he t radiation pick-up

He tin (s c as d rin si ver c rin or solderin ) may b harmful to certain fer ite materials

If this is the case, other me n for as urin go d thermal contact with the thermocouple

s ould b con idered

The next ste is to place two win in s on the core: the first is the se rc coi , con istin of a

sin le layer containin 2 0 turn of 0,2 mm diameter co p r wire, in ulated with a he t

resistant lac uer s c as p lyamide The win in s ould b spre d as evenly as p s ible

over the core ex lu in only the si ver-co ted p rt Then the drive coi is wou d on to of the

se rc coi The drive coi con ists of 7 turn of 0,5 mm diameter co p r wire, in uIated with

he t resistant lac uer The fig res given a ove s ould b ta en as examples only; other

n mb rs of turn may eq aly wel b u ed provided that they are ta en into ac ou t in the

calc lation

5.5 Me s rin a p ratus

The test sp cimen an a simi ar tran former (comp n ation u it , wou d on a non-mag etic

core of the same dimen ion as the fer ite toroid, are con ected to a me s rin circ it as

s own in Fig re 9 A sin soidal p wer source del verin 0 V to 5 V r.m.s with a freq en y

les than or eq al to 6 Hz is con ected to the primary win in s throu h a resistor R

i The

resistor is made of a s ort len th of con tantan wire an has, in the example given here, a

resistan e of 0,0 6 Ω (If care is exercised, the resistan e may b in re sed somewhat to

al ow for a lower sen itivity of the os i os o e X input.) The voltage dro acros the resistor

R

N

lH

RI

is the n mb r of primary turn

An input sig al of 1 V cor esp n s to a field stren th eq al to

im1

m

RlN

or, with the fig res u ed in the example q oted, 1 ,51 × 10

3

Am–1

Therefore, an os i os o e input voltage of 1 mV cor esp n s to a field stren th of 1 ,51 Am

–1

The output voltage from the two secon ary win in s, con ected in series, is pro ortional to

the time derivative of M To o tain a sig al pro ortional to M, it has to b integrated, whic is

4

= 1 MΩ

+ –

In order to have satisfactory p rforman e from the integrator, its ef ective time con tant RC ×

G (where G is the ampl fier gain) s al ex e d the reciprocal of the me s rin freq en y by a

factor of at le st 10 It s ould also b c eck d that the integrator do s not introd ce phase

CR

ANM

Uµ

e

/1/1

ln

rr

rh

–1

The b n width an sen itivity of the os i os o e s al b adeq ate A low- req en y l mit of

les than 0,2 Hz (prefera ly d.c.) an an up er l mit of more than 10 kHz wi give

satisfactory res lts The sen itivity of the X an Y ampl fiers s al ex e d 2 mm p r mi ivolt

The os i os o e Y input sig al is also ampl fied to a level of 10 V to 2 V an s bseq ently

rectified in a p a -sen in rectifier The rectified sig al is fed to the Y input of an X-Y-recorder

The X input of the recorder is fed by the thermocouples in s c a way that the recorder

deflection is directly pro ortional to the core temp rature in degre s Celsiu Th s a diagram

s owin the temp rature de en en e of M

Hcan b o tained

5.6 Cal bration

The os i os o e inputs are cal brated with the aid of an external, hig precision voltage

source The recorder is adju ted to cor ect sen itivity with regard to the temp rature interval

an the exp cted maximum value of M

temp rature This value ( hat is the width of the os i os o e display) s al b k pt con tant

IEC 6 5 6:2 0 +AMD1:2 16 CSV – 2 –

 IEC 2 16

5.7 Me s rin proced re

Al the electronic eq ipment s al b switc ed on a proximately 3 min b fore me s rement,

to en ure adeq ate sta i ty The test sp cimen is mou ted in the temp rature control ed test

c amb r an its win in s an thermocouple le d are con ected to the me s rin circ it

The X- an Y-amplfiers of the os i os o e are cal brated

The drive c r ent is in re sed so that the maximum mag etic field stren th is eq al to the

desired value, u ual y five times the co rcivity The sen itivity of the X-Y-recorder is adju ted

an its Y-axis calbrated again t the value of M re d of the os i os o e s re n

The temp rature of the test c amb r is brou ht down to the lowest temp rature of interest

The me s rement starts from this p int an the core temp rature is alowed to rise so slowly

( ypical y les than 3 °C/min) that the test sp cimen can b con idered to b in re sona le

thermal eq i brium The maximum value of M, (M

H), is automatical y recorded as a fu ction of

temp rature At certain temp ratures, re din s of remanent mag etization an co rcivity are

ta en Alternatively, photogra h may b ta en for more detai ed stu y of lo p config ration

The me s rement is terminated when the temp rature has re c ed an a pro riate value;

normal y a temp rature a l t le a ove the Curie p int is c osen

5.8 Calc lation

The os i os o e re din s, whether o tained from direct o servation or photogra h , are

converted into values of mag etization an field stren th u in the expres ion given in 5.5

The “s uarenes ratio”, M

rM

H, is calc lated u in the values th s o tained The recorder

c rve is self explanatory an req ires no further calc lation

5.9 Ac urac

The me s rin ac urac varies with M

H, the er or general y in re sin when a tran ition

temp rature is a pro c ed an M

H

b comes smal Suficiently far from these p ints, the

s stematic er or is, however, very smal , of the order of ± 1 %, provided that the me s rin

circ it is cor ectly bui t The u certainty introd ced by the re dout in trumentation is

ad itional to this This q antity may b very dific lt to esta ls , but the fol owin relative

er ors are typical of data o tained ac ordin to this method:

o tained by this method s al b q oted as fol ows:

– mag etization at a magnetic field stren th eq al to n times the co rcivity an at a

temp rature of θ °C: M kAm

–1

± 3 %;

or, in the case of remanent mag etization:

– remanent mag etization when the mag etic field stren th has b en decre sed from n

times the co rcivity to zero at a temp rature of θ °C: M kAm

is plot ed again t temp rature, the actual c rve s al b given together

with a statement con ernin the estimated ac urac

6 Gyromagnetic res nance linewidth ∆H and ef ectiv Landé factor g

ef(general)

6.1 General

The g romag etic resonan e l newidth an the ef ective L n é factor are pro erties whic are

of fu damental imp rtan e in determinin the p rforman e of devices o eratin at or ne r

g romag etic resonan e, an are neces ary for the computation of ten or p rme bi ty

comp nents in that region Determination of these q antities in olves the me s rement of a

resonan e phenomenon in whic b th freq en y an a pl ed mag etostatic field stren th are

critical p rameters Sta i ty, b th dimen ional (of the cavity) an electrical, th s b comes of

primary imp rtan e, p rtic larly when it comes to in estigatin materials havin very nar ow

resonan e lnewidth

6.2 Object

To des rib a method that can b u ed for me s rin the g romag etic resonan e l newidth

an the efective g- actor of isotro ic microwave fer ites over the a proximate freq en y

ran e 0,3 GHz to 3 GHz It may b u ed for materials havin wide as wel as nar ow

l newidth

6.3 The ry

The method a pl es ex lu ively to the so-caled Kitel s mode or u iform preces ion

resonan e; resonan es in whic other mag etostatic modes are in olved or whic s fer from

ambig ity d e to in uficient mag etic saturation are disregarded

The value of the field for maximum a sorption or resonan e H

0

may b the retical y computed

in terms of the saturation mag etization of the sample M

s, the demag etizin factors N

x, N

y,

If, on the other han , the sp cimen is s a ed as a disk with a diameter s f iciently larger than

its thicknes , an the external field is p rp n ic lar to the s rface, the formula b comes:

s0

0

0

31

2

MH

πγµ

T–1

s1

, it is th s p s ible, knowin f , H

0

s, to

calc late the ef ective L n é factor g

ef

The g romag etic resonan e l newidth ∆H is defined as the diferen e b twe n the two

mag etic field stren th values at whic the p wer a sorb d by the fer ite material is one-half

p rturb tion con e t, whic req ires that the sp cimen dimen ion s al b smal comp red

with the wavelen th in ide the sp cimen For disk sp cimen to b u ed over the freq en y

ran e 0,3 GHz to 3,0 GHz, the q otient of diameter an thicknes s al ex e d 3 with the

diameter me tin the req irement of 6.4

The a sorption in the sp cimen is me s red by determinin the c an e of p wer in ident on

the cavity req ired to k e the output p wer from the cavity at a fixed referen e level

The variation in input p wer may b expres ed as the variation of the aten ation in erted

b twe n the monitored source an the cavity in order to maintain the referen e output level If

of half the resonan e value, is given by one of the folowin eq ation :

lg

102lg

10

10/

0

1/2

r0

+

−+

=

−αα

precedin an the fol owin text

In p rtic lar, to en ure a s ficiently smal cavity p rturb tion, the me s red values of ∆H an

0

lg

HH

Q0,012αα

(2 )

where Q

0

is the Q value of the cavity without sp cimen

The sample dimen ion , for example the sphere diameter, s al b red ced u ti the los

dif eren e me ts this req irement

de en stron ly on the state of s rface of the samples Ide ly, they would b o tical y

p l s ed In practice, a ∆H -c rve may b ploted from thre ∆H me s rements cor esp n in

to thre progres ive stages of grin in , the as mptotic ∆H value b in q oted in 6.9 The

state of s rface of the sphere to b me s red may also b in irectly defined throu h the grain

size of the grin in a rasive

The p l s in proces may introd ce stres in the sample, af ectin the me s red value of ∆H

This efect may b minimized by an e l n for a s ort p riod of time

Tu in r od

(fu e si c ) Micr ometr e h a

spherical sp cimen is p sitioned at a p int of minimum electric an maximum mag etic

microwave field In Fig re 1 , the pro er sp cimen p sition is also in icated The sp cimen is

mou ted on a sample holder ( u ed si ca rod) The hole for in ertin the sp cimen into the

cavity is located in the nar ow cavity wal an s al not ex e d 2 mm in diameter ( or an

X-b n cavity) An ad itional p rturbin rod is mou ted in a s ita le p sition to al ow tu in by

interaction with the electric field in the cavity The input an output l nes to the cavity are

made to a p ar as matc ed lo d by me n of p d or isolators This typ of cavity desig

a pl es for spherical samples over the freq en y ran e of 3 GHz to 3 GHz If the me s rin

freq en y ex e d the value given by

s0

32

2

M

πγµ

(3 )

the o served value of ∆H wi contain contribution from the spin-wave modes ex ited by

defects of p ly ry tal ne fer ites [6]

For me s rements b twe n 0,3 GHz an 3 GHz, however, a disk-s a ed sp cimen is

prefera le The typ of cavity recommen ed, in this case, is a tu a le stripl ne resonator with

b th en s o en-circ ited as i u trated in Fig re 12 As is evident from the fig re, the cavity

has od -order resonan es at wavelen th of a out 2 , 2/3 where L is the len th of the

stripl ne in er con u tor

2

Dimen ion yieldin a lo ded q al ty factor (Q

0) gre ter than 4 0

are given for two freq en ies The sp cimen is glued to a sample holder whic is in the form

of a metal plu s rewed throu h the outer con u tor so that the sp cimen is located in the

vicinity of the centre of the in er con u tor To k e the microwave field as u iform as

p s ible over the sp cimen, the sample diameter s al b les than one- hird of the width of

the in er con u tor The tu in rod serves to tu e the cavity by ad itional p rturb tion so that

me s rement can b made at a predetermined freq en y Linewidth me s red on di

sk-s a ed sp cimen are not bro dened by spin-wave los

The pre arative proces may introd ce stres in the sp cimen afectin the me s red value

of ∆H This ef ect may b minimized by a proces of an e ln for a s ort p riod of time

6.5 Me s rin a p ratus

Fig re 13 is a s hematic diagram of the eq ipment req ired to ma e the me s rements

Power from a s ita le microwave source A o erated either u mod lated or with ampl tu e

mod lation, but fre from freq en y mod lation, is fed throu h a precision varia le at en ator

F to the cavity G, an the output p wer is detected an in icated on a s ita le meter H The

p wer in ident on the precision aten ator is monitored at E by me n of a directional coupler

an cry tal detector, an this in ident p wer is k pt con tant throu hout the me s rement by

me n of a varia le aten ator C The microwave freq en y, whic is monitored at B, can b

k pt u c an ed b cau e the tu in rod may b u ed to tu e the cavity to the generator

freq en y An adju ta le mag etic field of s f icient sta i ty p rp n ic lar to the microwave

mag etic field is a pl ed to the sp cimen The non-homogeneity of the a pl ed field over the

sp cimen s al b negl gible comp red to the l newidth b in me s red

6.6 Me s rin proced re

Set the generator freq en y as closely as p s ible to the me s rin freq en y Tu e the

cavity for maximum tran mis ion with the aid of the tu in rod Esta l s an input level

me s red at E, a setin α

0

on the precision at en ator, an an output level me s red at H

Ta e this output level as a referen e value

In ert the sp cimen into the cavity This o eration s ould have a negl gible efect on the

output level Ap ly the mag etic field an adju t it for maximum a sorption (minimum

tran mis ion) Determine the new setin α

r

on the precision at en ator whic restores the

output level to the referen e value Determine the microwave freq en y f an the a pl ed

mag etostatic field stren th H

0

—————————

2

Th use of a diele tric sample h ld r ma b prefere ; this wi n c s itate th use of a larg r sp cime for a

giv n se sitivity b t th lo atio of th sp cime within th o ter c n u tor is th n n t so critic l

gyromagnetic resonan e l newidth and ef ective Landé factor

The g romag etic resonan e l newidth may now b o tained by the fol owin method:

Meth d

Calc late the aten ator setin to o tain the referen e output level at the half p wer p ints

with the aid of eq ation (2 ) Set the precision aten ator at this value an vary the mag etic

field to o tain the referen e output level Retu e the cavity for maximum output with the aid of

the tu in rod Re dju t the field stren th an the tu in as req ired an note the final field

stren th value H

1 Re e t the proced re at the other half p wer p int to o tain H

2

In order to c eck sphericity an isotro y of spherical sp cimen , the sp cimen may b rotated

in the cavity The values o tained for H

0

an ∆H s ould not de en up n the sp cimen

orientation for cor ectly s a ed isotro ic materials Alowa le l mits of variation are 1 % of H

0

an 5 % of ∆H For thin disk sp cimen , the efect of the electromag etic mir or image up n

the me s red data s al b el minated prior to final me s rement This is ef ectively

ac ompls ed by ma in s c es ive me s rements on a sp cimen whose thicknes is varied

In most pra tic l c ses this c n itio is re c e for a giv n material with a p rtic lar v lu of th ratio ρ= d/D,

whic ma b d termin d fromth result of th pro e ure d scrib d Usu ly ρ< 1/ 10

6.7 Calc lation

The ef ective L n é factor is calc lated from o served values of freq en y an resonan e

field stren th ac ordin to Eq ation (2 ) (sphere) or Eq ation (2 ) (disk)

The g romag etic resonan e l newidth is calc lated as

21HH

6.8 Ac urac

If freq en y is me s red with an ac urac of ± 1 % an mag etic field stren th with an

ac urac of ± %, the relative er ors in the determination of ∆H an g

ef

b come eq al to

± % an ± %, resp ctively

6.9 Data presentation

Data s al b presented so as to conform with the req irements of IEC 6 3 2 The

me s rement freq en y s al b declared: this may b done by u in a s bs ript whic

re resents the me s rin freq en y in gigahertz, i.e ∆H

10, g

10 (if me s red at 10 GHz)

Information on the s a e an size of the sp cimen (spherical or disk-s a ed, dimen ion ) is

desira le, an its u iq e identity s al b given

Gyromag etic resonan e is c aracterized by an ef ective L n é factor an a resonan e

l newidth The me s rement of these q antities in olves b th freq en y an a pl ed

mag etostatic field as critical p rameters

Sta i ty, b th dimen ional (of the cavity) an electrical, th s b comes of primary imp rtan e,

p rtic larly with regard to materials havin very nar ow resonan e l newidth

7.2 Object

To des rib a method for me s rin g romag etic resonan e l newidth an efective L n é

factor of isotro ic microwave fer ites at a freq en y of 10 GHz It may b u ed for materials

havin wide as wel as nar ow l newidth

7.3 The ry

The method a ples ex lu ively to the u iform preces ion resonan e; s c resonan es in

whic mag etostatic modes of hig er order are in olved or whic s fer from ambig ity d e to

in uf icient mag etic saturation are disregarded

The value of the field for maximum a sorption or resonan e may b the retical y computed in

terms of the mag etization of the sample, the demag etizin factor, the ef ective L n é factor

200

s1

0

The g romag etic resonan e l newidth ∆H is defined as the diferen e b twe n the two

mag etic field stren th values at whic the p wer a sorb d by the fer ite material is one-half

the maximum a sorption

The method recommen ed for the me s rement of g

ef

an ∆H is b sed on the cavity

p rturb tion the ry The a sorption at resonan e is a proximately pro ortional to the

(saturation) mag etization divided by the resonan e l newidth If the a sorption b comes to

large to maintain the req ired ac urac , as may sometimes b the case with nar ow l newidth

materials, the sp cimen s ould b red ced in size To o tain les a sorption, the diameter (of

spherical samples) s ould b red ced as req ired (se 7.4)

The a sorption in the sp cimen is me s red by determinin the c an e of p wer in ident on

the cavity req ired to k e the output p wer from the cavity at a fixed referen e level

The variation in input p wer may b expres ed as the variation of at en ation in erted

b twe n the monitored source an the cavity in order to maintain the referen e or input level

of half the resonan e value, is given by one of the folowin eq ation :

1

10lg

102lg

+

−+

=

− )(

rαα

α

7.4 Test sp cimen and cavity

The test sp cimen for this method is a sphere Spherical sp cimen with a diameter not

gre ter than 1 mm wi give s ficient ac urac , provided that ∆H is gre ter than

0

0,01lg2

HH

Qα

2 0 0 The sp cimen is p sitioned away from the cavity wal s at a p int of minimum electric

an maximum mag etic microwave field Fig re 1 with the dimen ion for f = 10 GHz, s ows

a s ita le cavity in whic the pro er sp cimen p sition is in icated The sp cimen is mou ted

on a fu ed si ca (or other dielectric) rod The hole for in ertin the sp cimen into the cavity is

located in the nar ow cavity wal an s al not ex e d 2 mm in diameter An ad itional

p rturbin rod is mou ted in a s ita le p sition to alow tu in by interaction with the electric

field in the cavity The input an output l nes to the cavity are made to a p ar as matc ed

lo d by me n of p d or isolators This cavity desig a pl es for spherical samples, havin

diameters restricted ac ordin to the precedin p ragra h at a me s rin freq en y of

7.5 Me s rin a p ratus

Fig re 14 is a s hematic diagram of the eq ipment req ired to ma e the me s rements

Power from a s ita le microwave source A, o erated either u mod lated or with ampl tu e

mod lation, but fre from freq en y mod lation, is fed throu h a precision varia le at en ator

F to the cavity G, an the output p wer is detected an in icated on a s ita le meter H The

p wer in ident on the precision aten ator is monitored at E by me n of a directional coupler

an cry tal detector, an this in ident p wer is k pt con tant throu hout the me s rement by

me n of a varia le aten ator C The microwave freq en y, whic is monitored at B, can b

k pt u c an ed b cau e the p rturbin rod may b u ed to tu e the cavity to the generator

freq en y An adju ta le mag etic field of s f icient sta i ty p rp n ic lar to the microwave

mag etic field is a pl ed to the sp cimen The in omogeneity of the a pl ed field over the

sp cimen s al b negl gible comp red to the lnewidth b in me s red

7.6 Me s rin procedure

Set the generator freq en y as closely as p s ible to 10 GHz Tu e the cavity for maximum

tran mis ion with the aid of the dielectric rod Esta l s an input level me s red at E, a

set in α

0

on the precision aten ator, an an output level me s red at H Ta e this output

level as referen e value

In ert the sp cimen into the cavity This o eration s ould have neglgible ef ect on the output

level Ap ly the mag etic field an adju t it for maximum a sorption (minimum tran mis ion)

Determine the new set in α

r

on the precision aten ator whic restores the output level to the

referen e value Determine the microwave freq en y f

Calc late the aten ator setin to o tain the referen e output level at the half p wer p ints

with the aid of eq ation (3 ) Set the precision aten ator at this value an vary the mag etic

field to o tain the referen e output level Retu e the cavity for maximum output with the aid of

the dielectric rod Re dju t the field stren th an the tu in as req ired an note the final

field stren th value H

1 Re e t the proced re at the other half p wer p int to o tain H

2

of gyromagnetic resonance l newidth and ef ective Landé factor at 10 GHz

In order to c eck sphericity an isotro y of the sp cimen, the sphere may b rotated in the

cavity The values of field stren th me s red s ould not de en up n sp cimen orientation

for cor ectly s a ed isotro ic materials A variation of ±1 % d e to rotation may, however, b

tolerated

7.7 Calc lation

The efective L n é factor is calc lated from known values of freq en y an resonan e field

stren th ac ordin to Eq ation (3 )

The g romag etic resonan e l newidth is calc lated as

21HH

7.8 Ac urac

If freq en y is me s red with an ac urac of ±1 % an mag etic field stren th with an

ac urac of ± %, the relative er ors in the determination of ∆H an g

where the n mb rs p an q are given to thre sig ificant fig res

The re ort s al also in lu e the u iq e identity of the sample

8 Spin-wave resonance linewidth ∆H

k

8.1 General

Fer ite materials ex ibit an anomalou a sorption at hig r.f p wer levels that res lts from a

p wer de en ent coupl n b twe n the u iform mode of preces ion an spin-waves, or

throu h a direct coupln of r.f field to spin-waves Throu h this tran fer of energ , certain

spin-wave ampltu es bui d up The spin-wave freq en ies are eq al to one-half the a pl ed

freq en y or to the a pled freq en y The a sorption is o served when the spin-waves are

p rametrical y ex ited b yon some thres old level where u sta le growth of spin-wave

ampl tu e oc urs This thres old level, an hen e the relatively hig p wer p rforman e of

the fer ite material, can b s own to b related to the spin-wave l newidth ∆H

k

of the material

Spin-wave l newidth is an imp rtant pro erty of the material, an its determination is

neces ary to c aracterize the material completely Not only do the hig -p wer c aracteristic

of the materials de en on ∆H

k

but this l newidth is also in icative of los in a pl cation

where the material is biased far from resonan e For information a out spin-waves in general

an , in p rtic lar, a out their sig ifican e in microwave fer ite a plcation , se [7] an [8]

8.2 Object

The proced re des rib d p rmits the determination of the microwave spin-wave l newidth of

g romag etic materials The test is made at freq en ies ne r to 10 GHz, on spherical

samples at ro m temp rature Both mono- an p ly ry tal ne samples can b me s red by

this proced re In the case of monocry tal ne samples, ac ou t s al b ta en of the

orientation of the cry tal

The me s rement des rib d here is b sed on the so-caled p ral el pump tec niq e wherein

the sample is biased b low resonan e by a mag etostatic field a pled p ralel to the r.f field

In this ar an ement, the sample s ows low mag etic los at low r.f p wer levels The

thres old r.f field is determined by o servin the on et of non-l ne r los as eviden ed by a

c an e in s a e of the r.f pulse Althou h most devices o erate with p rp n ic lar hig

-freq en y an mag etostatic field , this method, employin p ral el pumpin for con enien e,

nevertheles gives res lts in icative of the los es at hig -p wer levels

For materials havin a large ∆H

k(of the order of 1 kAm

–1

, the on et of pulse deterioration

may b dific lt to o serve, ma in me s rement of µ″ as a fu ction of p wer a prefera le

method [7], where µ″ is the imaginary p rt of the complex p rme bi ty

8.3 The ry

The ex itation of spin-waves b yon the thres old level is o served either as an in re se in

los at mag etostatic field values b low that req ired for resonan e or as a saturation an

bro denin of the main resonan e l ne These efects are in icated in Fig re 15 Becau e the

s bsidiary resonan e ex ibits a more s arply defined thres old, more ac urate

me s rements of thres old level are p s ible in that region