Structural morphological and magnetic properties of al3 substituted ni0 25cu0 20zn0 55alxfe2 xo4 ferrites synthesized by solid state reaction route

The lattice constant, X-ray density and bulk density decrease while the porosity and grain size increase with the increase of Al content in the samples.. The frequency dependence of the

Structural, morphological and magnetic properties of Al 3+ substituted

Ni 0.25 Cu 0.20 Zn 0.55 Al x Fe 2
x O 4 ferrites synthesized by solid state reaction

route

K.R Rahmana, F.-U.-Z Chowdhurya,⇑, M.N.I Khanb

a

Department of Physics, Chittagong University of Engineering and Technology, Chittagong 4349, Bangladesh

b

Materials Science Division, Atomic Energy Center, Dhaka 1000, Bangladesh

a r t i c l e i n f o

Article history:

Received 7 September 2016

Accepted 27 December 2016

Available online 29 December 2016

Keywords:

X-ray diffractometry

Field emission scanning electron

microscopy

Initial permeability

Curie temperature

Vibration sample magnetometer

Magnetization

a b s t r a c t

Ni-Cu-Zn ferrite materials have been extensively used in electronic materials because of their outstand-ing properties at high frequencies This work investigates the impact of Al substitution on the structure, morphology and magnetic properties of Ni0.25Cu0.20Zn0.55AlxFe2
xO4(x = 0.00, 0.05, 0.10, 0.15 and 0.20) prepared by solid state reaction method X-ray diffractometer (XRD), field emission scanning electron microscope (FESEM), impedance analyzer and Vibrating Sample Magnetometer (VSM) were used to char-acterize the properties of the samples The XRD study confirmed the cubic spinel structure with single phase for all the samples The lattice constant, X-ray density and bulk density decrease while the porosity and grain size increase with the increase of Al content in the samples The frequency dependence of the complex permeability sintered at 1200°C has been measured for toroidal samples in the frequency range between 1 kHz and 120 MHz at room temperature The decrease in initial permeability has been explained on the basis of variation in grain size The temperature dependence of the initial permeability has been measured in the temperature range between from 30 to 250°C Curie temperature (Tc) has been estimated from the temperature dependence of the permeability spectra for all samples It is found that Curie temperatures and initial permeabilityðl0

iÞ decrease on Al substitution The saturation magnetiza-tion has been measured at room temperature and it was found to decrease with increasing of Al3+ions

Ó 2016 The Authors Published by Elsevier B.V This is an open access article under the CC BY-NC-ND

license (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Introduction

Ferrite materials have drawn a considerable attention to the

researchers for their soft magnetic properties and high frequency

application[1] The magnetic properties are highly responsive to

the technological parameters of ferrites especially on the amount

of metal oxides or additives in their constituent elements [2]

Important and interesting electrical and magnetic properties of

spinel ferrites depend on a proper selection of cations along with

Fe2+, Fe3+, and their sharing in the tetrahedral (A) and octahedral

(B) sites of spinel lattice [3] The magnetic properties of

Zn-substituted ferrites have a considerable position because of the

importance of these materials for high frequency applications

Though zinc ferrites (ZnFe2O4) have normal spinel structure, i.e.,

(Zn2+)A[Fe3+

2]BO2
4 where all Zn2+ions reside on A-sites and Fe3+ions

on B-sites, the substitution of Cu by Zn in Cu1
xZnxFe2O4 is

pre-dictable to change the magnetic behavior The nature of

magnetiza-tion and magnetic ordering of Zn substituted ferrites have been studied by many researchers[4–7] It has been reported that Cu is used in NiCuZn ferrite to get better densification as well as electro-magnetic properties[8] It is observed that the transition tempera-ture increased with an increasing Ni concentration [9] Some researchers worked on NiCuZn ferrites, especially to appreciate the best possible concentrations that cooperation with the electrical and magnetic properties[10–14] Al substituted Ni-Zn ferrite has been prepared by standard double sintering method and the struc-tural, electrical, dielectric and magnetic Properties have been studied

by Raut et al.[15]They found that the lattice constant increases while the saturation magnetization decreases with the increase in

Al concentration Hossain et.al observed that both lattice constant and average grain size have decreased due to addition of Al in Ni0.27

-Cu0.10Zn0.63AlxFe2
xO4[16] It has been found that both initial per-meability and saturation magnetization were increased significantly at a small fraction of La (0.025) substitution[17]

In this article, the reports are essentially focused on synthesis and detailed study of the structural, morphological and magnetic properties of Al-substituted Ni0.25Cu0.20Zn0.55AlxFe2
xO4ferrites

http://dx.doi.org/10.1016/j.rinp.2016.12.045

2211-3797/Ó 2016 The Authors Published by Elsevier B.V.

⇑Corresponding author.

E-mail address: faruque@cuet.ac.bd (F.-U.-Z Chowdhury).

Contents lists available atScienceDirect

Results in Physics

j o u r n a l h o m e p a g e : w w w j o u r n a l s e l s e v i e r c o m/ r e s u l t s - i n - p h y s i c s

Polycrystalline ferrites with the nominal composition of Ni0.25

-Cu0.20Zn0.55AlxFe2
xO4 (x = 0.00, 0.05, 0.10, 0.15 and 0.20) were

prepared by conventional solid state ceramic method Analytical

grade high purity nitrate salts of Sigma-Aldrich, UK, were used as

raw materials Proper stoichiometric ratios of the reagent of

ana-lytical grade NiO, CuO, ZnO, Al2O3 and Fe2O3 were mixed

thor-oughly in an agate mortar for 5 h to achieve homogeneity in the

mixed powder The mixture was calcinated in air at 800°C in a

fur-nace (NABER HTCT 08/16) for 3 h and then cooled without any

external aid After calcination the sample, the chunk of the sample

was ground into very fine powder using an agate mortar for 2 h

The powder was mixed up with a small quantity of polyvinyl

alco-hol as binder and was pressed (1 kN/m2) by a hydraulic press into

compacts of disk and toroid shapes Finally, sintering was

per-formed using a programmable furnace NABER (HTCT 08/16) at

1200°C for 3 h with the temperature ramp of 5 °C/min for both

heating and cooling

X-ray diffraction study was done using a Philips PANalytical

X’pert PRO X-ray diffractometer with CuKa radiation

(k = 1.5418 Å) in order to perform the structural analysis The

diffraction data were recorded between 15° and 70° in steps of

0.02° at time for each step data collection was 1.0 s at room

tem-perature The lattice constant ‘a’ of each sample was calculated

from the relation: a¼ dðh2

þ k2

þ l2

Þ1=2, where d and (hkl) repre-sent the interplanar distance and Miller indices, respectively The

lattice parameter for each sample was estimated using

Nelson-Riley function[18] The X-ray density (qx), was calculated using

the relation,qx= 8M/Na3, where M is the molecular weight of the

composition and N is Avogadro’s number The bulk density,

qB= m/V, was determined from the mass (m) and volume (V = a3)

of the cubic unit cell The porosity (P) of any composition was

cal-culated applying the relation: P(%) = (qx
qB)/qx)100

The morphologies of the samples were examined using a field

emission scanning electron microscope (FESEM) (model: JEOL

JSM-7600 F) The average grain size of each component was

deter-mined from micrographs by linear intercept technique

The complex initial permeability of the toroid-shaped samples

was measured using an impedance analyzer of Wayne Kerr

(6500B) at room temperature over a frequency range 1 kHz–

120 MHz The Curie temperature measurements have been done

by an inductance analyzer from Wayne Kerr (3255B) at 100 kHz

in the temperature range from 30 to 250°C The real ðl0

iÞ and imag-inary partðl00

iÞ of the complex initial permeability were computed using the relationsl0

i¼ Ls=L0where, Lsis the self-inductance of the sample core, Lorepresents the inductance of the winding coil with-out the sample core,l00¼l0tan d L ¼l N2S=pd, where N is the

(311)

x=0.20 x=0.15

x=0.10

x=0.05

x=0.0

2θ (degree) Fig 1a X-ray diffraction patterns of Ni 0.25 Cu 0.20 Zn 0.55 Al x Fe 2
x O 4 (0.0 6 x 6 0.2)

sintered at 1200 °C.

34.0 34.5 35.0 35.5 36.0 36.5 37.0

(311)

x=0.20

x=0.15

x=0.10

x=0.05 x=0.0

2θ (degree) Fig 1b The magnified XRD peak corresponding to the plane (3 1 1) of

Ni 0.25 Cu 0.20 Zn 0.55 Al x Fe 2
x O 4 (0.0 6 x 6 0.2) sintered at 1200 °C.

8.46 8.47 8.48

8.49

lattice constant porosity

12 14 16 18

Fig 2 The variation of lattice constant (a 0 ) and porosity (P) with Al content (x) of

Ni 0.25 Cu 0.20 Zn 0.55 Al x Fe 2
x O 4 (0.0 6 x 6 0.2) sintered at 1200 °C.

Table 1 The variation of lattice constant (a 0 ), X-ray density (qx ), bulk density (qb ) , porosity (P) and average grain size (D) of Ni 0.25 Cu 0.20 Zn 0.55 Al x Fe 2
x O 4 with different Al content (x) sintered at 1200 °C.

x a 0 (Å) qx (gm/cm 3 ) qb (gm/cm 3 ) P (%) D (lm)

number of turns of the coil (N = 5), S equal tod 1
d 2

2  h where, d1, d2

and h represent outer (1.14 cm) and inner (0.66 cm) diameters and

height (0.31 cm) of the toroid shaped sample, respectively S and

d ¼d1þd 2

2

represent the cross-sectional area and mean diameter

of the toroid-shaped sample, respectively The relation,

Q¼l0

i= tan d, where tand is the loss factor, was used to calculate the relative quality factor, Q

To measure the magnetization behavior of the prepared sam-ples, the field dependence magnetization has been measured at room temperature by using Vibrating Sample Magnetometer (VSM) (Model EV7)

Fig 3 (a–e) FESEM micrographs of Ni Cu Zn Al Fe O system sintered at 1200 °C (2000).

Results and discussion

Structural analysis

Al-substituted composites with chemical formula Ni0.25Cu0.20

-Zn0.55AlxFe2
xO4 (x = 0.00, 0.05, 0.10, 0.15 and 0.20) sintered at

1200°C in air for 3 h, have been prepared by the solid state

reac-tion technique TheFig 1ashows the indexed peaks of all samples

as revealed from the XRD patterns The well-defined sharp peaks in

the spectra are the indication of polycrystalline behavior with good

crystallinity The peaks have been indexed as (1 1 1), (2 2 0),

(3 1 1), (2 2 2), (4 0 0), (4 2 2), (5 1 1) and (4 4 0), which are the

characteristics of cubic single phase spinel structure of the samples

belonging to the space group Fd3m From the XRD patterns it is

observed that the peak positions match with the earlier report

and no traces of impurities were found[19] The magnified XRD

peak located at around 2h–35°Corresponding to plane (311) of

the samples are presented in (Fig 1b) The shifting of this peak

towards low angle region of Al-substituted NiCuZnAl ferrites

indi-cates the replacement of Fe ions by Al ions Nelson-Riley

extrapo-lation method was used to find out the exact lattice constant (a0)

and the Nelson-Riley function F(h) is given as[18]:

2

h

where, h is the Bragg’s angle The values of lattice parameter (a) of

all the peaks for each sample were plotted against F(h) The exact

value of lattice constant, a0for each sample was estimated from

the extrapolation of the straight line obtained from the least square

fit method at F(h) = 0

The variation of lattice constant (a0) and porosity with Al

con-tent is shown inFig 2 Decrease in lattice constant is observed with

increasing Al concentration and it could be explained on the basis

of ionic radius where the substitution of smaller Al3+ion (0.535 Å)

for large Fe3+ ion (0.645 Å) in the NiCuZnAl system [20] The

increase in porosity with Al addition might be due to the

replace-ment of Fe3+by Al3+, which leaves relatively more empty spaces in

the samples

The values of lattice constant (a0), X-ray density (qx), bulk

den-sity (qB), porosity (P) and average grain size (D) of the samples

sin-tered at 1200°C for 3 h are summarized in Table 1 From the

4.24 gm/cm3 as Al3+ concentration (x) is increased from 0.0 to

0.20 in the series This can be explained in terms of the difference

between the atomic weight of Fe3+and Al3+ Al has smaller atomic

weight (26.98 amu) as compared to Fe (55.85 amu) The decrease

in X-ray density from 5.19 gm/cm3to 5.12 gm/cm3with increasing

Al contents in the samples is observed and it might be due to the

decrease in volume of the unit cell[21] The difference between

two types of density ensures the presence of pores in the samples

Surface morphology

Typical micrographs (2000) obtained by field emission

scan-ning electron microscopy (FESEM) of NiCuZnAl ferrite system

sin-tered at 1200°C for 3 h are shown in Fig 3(a–e) The FESEM

characterization is used to see the microstructure character of

the prepared ferrites The FESEM micrographs show non-uniform

grains with an average grain size in the range from 7.39 to

23.03lm as estimated using the linear intercept method which

depends on the Al content[22] The increase in grain size is an

indication that more pores exist when Al3+ concentrations is

increased in the composite[16] The addition of Al improves the

increase of the average grain size at the same time with porosity

increase

Curie temperature The temperature stability of initial permeability ðl0

iÞ is very important for designing a magnetic material The Curie tempera-ture (Tc) is an important magnetic property and is a compositional dependent parameter The temperature at whichl0

iabruptly drops

is considered as the Curie temperature The initial permeability as

a function of temperature of the toroid-shaped samples are shown

iinitially remains steady with the rise of tempera-ture and then falls sharply near the Curie temperatempera-ture, Tc [23] The curves are typical of multi-domain grains showing a sudden drop in the values ofl0

iat the Curie temperature which is deter-mined at the rapid decrease ofl0

i It is evident that the decrease can be attributed to the decrease in saturation magnetization At

Tc, Ms drops sharply with temperature leading to the rapid decrease inl0

i A similar trend of Tcvalue is reported for Al substi-tution in MgCuZn ferrite[24,25] The variation of Curie tempera-ture on the Al concentration of the samples is shown inFig 5 It

is seen that the Curie temperature decreases with increasing Al concentration The decrease in Curie temperature is due to decrease of A-B interactions resulting from Fe replacement by Al

on tetrahedral sites[26] The increasing or decreasing trend of Tc

depends on the distance between the moments of A- and B-sites, i.e the number of magnetic ions presents in the two sublattices

100 200 300 400 500 600 700

0.0 0.05 0.10 0.15 0.20

Fig 4 Variation of initial permeability with temperature for the spinel system

Ni 0.25 Cu 0.20 Zn 0.55 Al x Fe 2
x O 4 (0.0 6 x 6 0.2) sintered at 1200 °C.

100 120 140 160

T c (

o C)

Al concentration, x

Fig 5 The variation of Curie temperature (T c ) with the Al concentration (x) of the samples Ni Cu Zn Al Fe O sintered at 1200 °C.

Hysteresis loop study

It is a common practice to analyze dynamic magnetic hysteresis

loop for describing the magnetic behavior of soft ferrites The

vari-ation of magnetizvari-ation (M) as a function of applied field (H) at

room temperature for all samples at 1 kHz is depicted inFig 6

(a–e) It is clear that the magnetization increases with increasing

applied field and attains its saturation which is similar to any soft

magnetic materials It has been found that the increase of Al3+

con-centration contributes to the decrease of saturation magnetization

(Ms) and coercive magnetic field strength The saturation

magneti-zation has a maximum value for the sample x = 0, whereas it

decreases with Al addition The increase in Al content in the

sam-ples might be described as the improvement in collinearity

between A-B interaction, further replacement of Fe3+by

nonmag-netic Al3+ leads to decrease B-site magnetic moment as well as

increase in porosity and therefore decreasing net magnetic

moment The composition dependence of saturation

magnetiza-tion is shown inFig 7 The decrease in saturation magnetization

is more when nonmagnetic Al present in the samples is higher

The saturation magnetization, remanent magnetization, coercivity and Curie temperature are tabulated inTable 2

Complex permeability and relative quality factor The real component of permeability ðl0

iÞ as a function of fre-quency (up to 120 MHz), at room temperature for Ni0.25Cu0.20

-Zn0.55AlxFe2
xO4ferrites, is presented inFig 8 It is found thatl0

i

is reasonably constant at low frequencies with a maximum of

535 and 165 at 1 kHz for x = 0.0 and 0.20, respectively, and then decreases very fast at high frequency (120 MHz) It is observed that except x = 0.0, initial permeability of all the samples shows an almost flat profile from 1 kHz to 10 MHz This constantl0

i value over a wide frequency range indicates the compositional stability and quality of ferrites prepared using solid state reaction tech-nique The flat region up to the frequency from where it begins

to fall quickly is recognized as the area of utility of the ferrites The frequency at whichl0

iattains the highest value and thereafter decreases, is recognized as the resonance frequency, fr[27] The resonance frequency is shifted towards higher frequency with

-40 -20 0 20 40

H (Oe)

x= 0.0

-30 -20 -10 0 10 20 30

H (Oe)

x=0.05

-20 -10 0 10 20

H (Oe)

x=0.10

-20 -10 0 10 20

H (Oe)

x=0.15

-20 -10 0 10 20

H (Oe)

x=0.20

(e)

Fig 6 (a–e) Magnetic hysteresis loops (measured at room temperature) for the spinel system Ni Cu Zn Al Fe O (0.0 6 x 6 0.2) sintered at 1200 °C.

addition Al content Two kinds of mechanisms of magnetization

namely, spin rotation and domain wall motion, contribute in the

complex permeability of these types of ferrites In the low

fre-quency region, the contribution of spin rotation is not noteworthy

than domain wall motion The spin rotation is essentially due to

reversible motion of domain walls in the presence of a weak

mag-netic field The effect of domain wall motion on permeability can

be explained by the Globus relation[28]: l0

i¼ M2

sD=pffiffiffiffiffiffiK1

, where

D is the average grain size, and K1is the magneto-crystalline

aniso-tropy constant As domain wall motion is significantly influenced

by grain size, its role to the permeability is enhanced with the

increase in grain size Dispersion occurs because the domain wall

motion plays a relatively important role when the spin rotation

reduces[29] Permeability decreased due to weak A-B interaction

The dependence of permeability is proportional to the force on a

domain wall caused by a magnetic field and the resultant change

of magnetization

The frequency dependence imaginary permeabilityl00

i, for the samples is shown in Fig 9 The imaginary component rises and making a peak at a certain frequency wherel0

i falls rapidly[30]

It is evident from the figure that thel00

i falls rapidly up to 105Hz and then remained almost constant up to 1.20 MHz After this fre-quency,l00

i gradually increased with increasing frequency with a broad maximum at a frequency (shown in the inset of Fig 9), where thel0

i rapidly decreased, recognized as the dispersion of

l0

i This could be attributed due to either domain wall displacement

or domain rotation or the combined effect of these contributions [31], is known as cutoff frequency[32] The cutoff frequencies cor-responding to the peaks ofl00

i are the results of the absorption of energy due to matching of the oscillation frequency of the mag-netic dipoles and the applied frequency

15

20

25

30

35

40

45

Al concentration, x

Fig 7 The dependence of saturation magnetization (M s ) on Al content (x) of

Ni 0.25 Cu 0.20 Zn 0.55 Al x Fe 2
x O 4 sintered at 1200 °C.

Table 2

Variation of saturation magnetization (M s ), remanent magnetization (M r ), M r /M s , coercivity (C r ), Curie temperature (T c ) and initial permeability ðl0

i Þ with different Al content (x) of

Ni 0.25 Cu 0.20 Zn 0.55 Al x Fe 2
x O 4 sintered at 1200 °C.

i

0

100

200

300

400

500

600

Frequency (Hz)

0.0 0.05 0.10 0.15 0.20

Fig 8 Variation of the real part of permeability ðl0

i Þ with frequency of

Ni Cu Zn Al Fe O (0.0 6 x 6 0.2) sintered at 1200 °C.

0.0 500.0 1.0k 1.5k 2.0k 2.5k

Frequency (Hz)

0.00 0.05 0.10 0.15 0.20

Fig 10 Variation of relative quality factor (RQF) with frequency for

Ni Cu Zn Al Fe O (0.0 6 x 6 0.2) sintered at 1200 °C.

103 104 105 106 107 108 0

100 200 300 400

1M 10M 100M 20

40 60 80 100 120 140

Frequency Hz

0.0 0.05 0.15

μ// ι

Frequency (Hz)

0.0 0.05 0.10 0.15 0.20

Fig 9 Variation of the imaginary part of permeability ðl00

i Þ with frequency of

Ni 0.25 Cu 0.20 Zn 0.55 Al x Fe 2
x O 4 (0.0 6 x 6 0.2) sintered at 1200 °C.

From the loss factor, we have calculated the relative quality

fac-tor (Q-facfac-tor), i.e Q¼l0

i= tan d for all the compositions which is shown inFig 10 It determines of the quality or performance of a

material From the figure it is observed that Q-factor rises with

the increase in frequency having a peak and then it falls with

fur-ther increase in frequency It is also revealed from the figure that

the values of Q-factor of Al substituted ferrites are slightly lower

than that of sample with x = 0.0 This might be due to higher

hys-teresis loss of the sample which increases with an increase in

porosity [33] Porosity works as an extra pinning center which

obstructs the motion of domain wall As a consequence, higher

magnetic field is necessary to switch the domain wall motion,

resulting higher hysteresis losses[34]

Conclusions

Al substituted Ni0.25Cu0.20Zn0.55AlxFe2
xO4(x = 0.00, 0.05, 0.10,

0.15 and 0.20) ferrites have been successfully prepared by the solid

state reaction method The prepared samples, sintered at 1200°C,

were characterized for structural, morphological and magnetic

properties The XRD patterns of the samples showed the existence

of characteristic peaks validating the formation of single phase

cubic spinel structure Lattice constant, bulk density, X-ray density

decreases with increasing Al content, whereas the average grain

size and porosity show the opposite trend The Curie temperature

and initial permeability at room temperature also decrease with Al

addition and are strongly depending on the average grain size,

den-sity and poroden-sity Saturation magnetization decreases with the

increase of Al substitution which is due to the dilution A-B

interac-tion Magnetic measurements confirm the formation of

magneti-cally soft materials The relative quality factors of the prepared

samples decrease with Al content which is due to the decrease of

saturation magnetization The hysteresis loops of the samples were

measured at room temperature and the consequences of Al

substi-tution on the saturation magnetization, coercivity and remanent

magnetization were observed From the frequency characteristic

of Q-factor the perfect frequency band can be identified in which

these materials work well as a soft magnetic material with low

losses

Acknowledgements

The authors express their gratitude to the authority of the

Materials Science Division (MSD), Atomic Energy Centre, Dhaka

(AECD), Bangladesh The authors express their heartfelt thanks to

the authority of Chittagong University of Engineering and

Technol-ogy, Chittagong 4349, Bangladesh for their continual support

References

[1] Shobana MK, Sankar S, Rajendran V Characterization of Co 0.5 Mn 0.5 Fe 2 O 4

nanoparticles Mater Chem Phys 2009;113:10–3 http://dx.doi.org/10.1016/

j.matchemphys.2008.07.083

[2] Caltum OF, Spinu L, Stancu AI, Thung LD, Zhou W Study of the microstructure

and of the permeability spectra of Ni-Zn-Cu ferrites J Magn Magn Mater

2002;242–245 http://dx.doi.org/10.1016/S0304-8853(01)01187-8 162–162.

[3] Gul IH, Maqsood A Structural, magnetic and electrical properties of cobalt

ferrites prepared by the sol-gel route J Alloys Compd 2008;465(1–2):227–31.

http://dx.doi.org/10.1016/j.jallcom.2007.11.006

[4] Petitt GA, Forester DW Mössbauer study of cobalt-zinc ferrites Phys Rev B

1971;4:3912

[5] Kulkarni RG, Patil VU Magnetic ordering in Cu-Zn ferrite J Mater Sci

1982;17:843 http://dx.doi.org/10.1007/BF00540382

[6] Murthy NSS, Natera MG, Youssef SI, Begum RJ, Srivastava CM Yafet-Kittel

angles in zinc-nickel ferrites Phys Rev 1969;181:969–77 http://dx.doi.org/

10.1007/BF00540382

[7] Haque M, Huq M, Hakim MA Effect of Zn 2+

substitution on the magnetic properties of Mg 1
x Zn x Fe 2 O 4 ferrites Physica B 2009;404:3915 http://dx.doi.

org/10.1016/j.physb.2009.07.124

[8] Modak S, Ammar M, Mazaleyrat F, Das S, Chakrabarti PK XRD, HRTEM and magnetic properties of mixed spinel nanocrystalline Ni-Zn-Cu-ferrite J Alloys Compd 2009;473:15–9 http://dx.doi.org/10.1016/j.jallcom.2008.06.020 [9] Kaiser M Effect of nickel substitutions on some properties of Cu-Zn ferrites J Alloys Compd 2009;468:15–21 http://dx.doi.org/10.1016/ j.jallcom.2008.01.070

[10] Yue Z, Zhou J, Li L, Gui ZJ Effects of MnO 2 on the electromagnetic properties of NiCuZn ferrites prepared by sol-gel auto-combustion Magn Magn Mater 2001;233:224–9 http://dx.doi.org/10.1016/S0304-8853(01)00200-1 [11] Gabal MA Effect of Mg substitution on the magnetic properties of NiCuZn ferrite nanoparticles prepared through a novel method using egg white J Magn Magn Mater 2009;321:3144–8 http://dx.doi.org/10.1016/j jmmm.2009.05.047

[12] Roy PK, Bera J Electromagnetic properties of samarium-substituted NiCuZn ferrite prepared by auto-combustion method J Magn Magn Mater 2009;321:247–51 http://dx.doi.org/10.1016/j.jmmm.2008.08.051

[13] Hu J, Yan M Preparation of high-permeability NiCuZn ferrite Zhejiang Univ Sci 2005;6B:580–3 http://dx.doi.org/10.1631/jzus.2005.B0580

[14] Su H, Zhang H, Tang X, Zhong Z, Jing Y Analysis of low-temperature-fired NiCuZn ferrites for power applications J Mater Sci Eng B 2009;162:22–5.

http://dx.doi.org/10.1016/j.mseb.2009.01.030 [15] Raut AV, Khirade PP, Humbe A, Jadhav SA, Shengule DR Structural, electrical, dielectric and magnetic properties of Al 3+ substituted Ni-Zn ferrite J Supercond Novel Magn 2016;29:1331–7 http://dx.doi.org/10.1007/s10948-016-3421-6

[16] Hossen MB, Hossain AKMA Influence of Al3 + substitution on impedance spectroscopy studies of Ni 0.27 Cu 0.10 Zn 0.63 Al x Fe 2
x O 4 Adv Mater Lett 2015;6 (9):810–5 http://dx.doi.org/10.5185/amlett.2015.5854

[17] Roy PK, Nayak BB, Bera J Study on electro-magnetic properties of La substituted Ni-Cu-Zn ferrite synthesized by auto-combustion method J Magn Magn Mater 2008;320:1128–32 http://dx.doi.org/10.1016/j jmmm.2007.10.025

[18] Nelson JB, Riley DP An experimental investigation of extrapolation methods in the derivation of accurate unit-cell dimensions of crystals Proc Phys Soc London 1945;57:160–77 http://dx.doi.org/10.1088/0959-5309/57/3/302 [19] Ghodake SA, Ghodake UR, Sawant SR, Suryavanshi SS, Bakare PP Magnetic properties of NiCuZn ferrites synthesized by oxalate precursor method J Magn Magn Mater 2006;305:110–9 http://dx.doi.org/10.1016/j.jmmm.2005.11.041 [20] Ramay SM, Siddique SA, Atiq S Structural, magnetic, and electrical properties

of Al 3+

substituted CuZn-ferrites Chin J Chem Phys 2010;23:591–5 http://dx doi.org/10.1088/1674-0068/23/05/591-595

[21] Hossen MB Hossain AKMA Structural and dynamic electromagnetic properties of Ni 0.27 Cu 0.10 Zn 0.63 Al x Fe 2
x O 4 J Magn Magn Mater 2015;387:24–36 http://dx.doi.org/10.1016/j.jmmm.2015.03.083

[22] Eltabey MM, El-Shokrofy KM, Gharbia SA Enhancement of the magnetic properties of Ni-Cu-Zn ferrites by the non-magnetic Al 3+ -ions substitution J Alloys Compd 2011;509:2473–7 http://dx.doi.org/10.1016/ j.jallcom.2010.11.056

[23] Ateia E, Ahmed MA, Ghouniem RM Electrical properties and initial permeability of Cu-Mg ferrites Solid State Sci 2014;31:99–106 http://dx.doi org/10.1016/j.solidstatesciences.2014.03.002

[24] Globus A, Pascard H, Cagan VJ Distance between magnetic ions and fundamental properties in ferrites J Phys 1977;38 http://dx.doi.org/10.1051/ jphyscol:1977132 C1-163–C1-168.

[25] Bahiraei H, Shoushtari MZ, Gheisari K, Ong CK The effect of non-magnetic Al 3+

ions on the structure and electromagnetic properties of MgCuZn ferrite J Magn Magn Mater 2014;371:29–34 http://dx.doi.org/10.1016/j.jmmm.2014.07.003 [26] Chikazumi S, Charap SH Physics of magnetism, 93 New York: John Wiley and Sons Inc; 1964

[27] Nam JH, Jung HH, Shin JY, Oh JH The effect of Cu substitution on the electrical and magnetic properties of NiZn ferrites IEEE Trans Magn 1995;31:3985–7.

http://dx.doi.org/10.1109/20.489838 [28] Globus A, Duplex P, Guyot M Determination of initial magnetization curve from crystallites size and effective anisotropy field IEEE Trans Magn 1971;7:617–22 http://dx.doi.org/10.1109/TMAG.1971.1067200

[29] Maria KH, Choudhury S, Hakim MA Structural phase transformation and hysteresis behavior of Cu-Zn ferrites Inter Nano Lett 2013;3(1):42 http://dx doi.org/10.1186/2228-5326-3-42

[30] Lakshman A, Rao PSVS, Rao KH Frequency dependence of initial permeability and magnetic loss factor of In 3+ and Cr 3+ substituted Mg-Mn ferrites J Magn Magn Mater 2004;283:329–34 http://dx.doi.org/10.1016/j jmmm.2004.05.040

[31] Rado GT, Wright RW, Emerson WH Ferromagnetism at very high frequencies III Two mechanisms of dispersion in a ferrite Phys Rev 1950;80:273–80 [32] Nakamura T Low-temperature sintering of Ni-Zn-Cu ferrite and its permeability spectra J Magn Magn Mater 1997;168:285–91 http://dx.doi org/10.1016/S0304-8853(96)00709-3

[33] Néel L Magnetic properties of ferrites: ferrimagnetism and antiferromagnetism Ann Phys 1948;3:137–47

[34] Zahir R, Chowdhury F-U-Z, Uddin MM, Hakim MA Structural, magnetic and electrical characterization of Cd-substituted Mg ferrites synthesized by double sintering technique J Magn Magn Mater 2016;410:55–62 http://dx.doi.org/ 10.1016/j.jmmm.2016.03.019