DSpace at VNU: Magnetocaloric effect in Fe-Ni-Zr alloys prepared by using the rapidly-quenched method

Magnetocaloric Effect in Fe-Ni-Zr Alloys Preparedby Using the Rapidly-quenched Method Nguyen Huy Dan,∗ Nguyen Huu Duc, Tran Dang Thanh, Nguyen Hai Yen and Pham Thi Thanh Institute of Mate

Magnetocaloric Effect in Fe-Ni-Zr Alloys Prepared

by Using the Rapidly-quenched Method

Nguyen Huy Dan,∗ Nguyen Huu Duc, Tran Dang Thanh, Nguyen Hai Yen and Pham Thi Thanh Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Hanoi, Vietnam

Ngac An Bang and Do Thi Kim Anh

Hanoi University of Science, 334 Nguyen Trai, Hanoi, Vietnam

The-Long Phan and Seong-Cho Yu† Chungbuk National University, Cheongju 361 - 763, South Korea

(Received 31 May 2012, in final form 21 July 2012)

Fe90−xNixZr10 (x = 0, 5, 10, 15, 20 and 25) ribbons with various thicknesses were prepared by

using a melt-spinning technique The Curie temperature, T C, of the alloys dramatically decreased

from∼960 K to room temperature at high quenching rates When the alloys had an amorphous

structure, their T C strongly depended on the Ni concentration The maximum entropy change,

|∆S m | max , with ∆H = 12 kOe, of the alloys was around 1 J·kg −1K−1 at room temperature On

the other hand, the full width at half maximum the entropy-change peak was quite large,∼ 85 K,

which was suitable for applications in magnetic refrigerators at room temperature

PACS numbers: 75.30.Sg, 07.20.Mc, 75.50.Kj

Keywords: Magnetocaloric effect, Refrigeration, Amorphous magnetic materials

DOI: 10.3938/jkps.62.1715

I INTRODUCTION

The giant magnetocaloric effect (GMCE) in materials

is of interest in research virtue of its potential

applica-tions in the field of magnetic refrigeration Magnetic

re-frigeration is based on the principle of magnetic entropy

change in materials under a varying magnetic field The

application of magnetocaloric materials in refrigerators

has the advantages of avoiding environmental pollution

(unlike the refrigerators using compressed gases),

im-proving the cooling efficiency (saving energy), reducing

noise, and fitting some special cases The main problems

to be addressed to improve the practical applications of

magnetocaloric materials are: i) creating the GMCE in a

low field, because creating a large magnetic field in civil

devices is very difficult, ii) taking the magnetic phase

transition temperature (working temperature) of

mate-rials with the GMCE to room temperature, and iii)

ex-tending the working temperature range (range with the

GMCE) for materials to be cooled to a large temperature

range In addition, some other properties of materials,

such as the heat capacity, electrical conductivity,

ther-mal conductivity, durability, price,etc., also need to be

∗E-mail: dannh@ims.vast.ac.vn

†E-mail: scyu@chungbuk.ac.kr

addressed for the application of GMCE materials Along with the goal of saving energy and protecting the environmental, searches for magnetocaloric mate-rials with capabilities for applications in magnetic re-frigeration at room temperature are increasingly of in-terest in research Notably, the results obtained for

Gd-containing magnetocaloric alloys (GdSiGe, GdCo .)

[1, 2] have shown capabilities for extensive applications

of magnetic refrigeration technology A number of de-vices using magnetic refrigerants have been experimen-tally produced with Gd-containing magnetocaloric al-loys However, Gd-containing alloys have very high costs due to the scarcity of raw materials and the strict manufacturing technology In addition, Gd-containing alloys do not satisfy a number of other requirements such as strength and thermal conductivity Besides Gd-containing alloys, some of other magnetocaloric materials are of interest in studies on the mechanisms and possible applications These materials include As-containing

al-loys (MnAsSb, MnFePAs .) [3,4], La-containing alal-loys (LaFeSi), Heusler alloys (CoMnSi, NiMnSn, NiMnGa .)

[5,6] and ferromagnetic perovskite maganites [7,8] Recently, many researchers have focused on magne-tocaloric materials with amorphous or nanocrystalline structures [9–12] The main advantages of amor-phous or nanocrystalline materials are their capabilities

-1715-for the GMCE, low coercivity, high resistivity,

room-temperature magnetic phase transition and low cost,

which are necessary requirements for practical

applica-tions Among this kind of GMCE materials, the

Fe-Zr-based alloys have been attracting the attention of many

scientists [13–19] In this work, we investigate the

mag-netocaloric effect in Fe-Ni-Zr alloys prepared by using

the rapidly-quenched method

II EXPERIMENTS AND DISCUSSION

The alloys with nominal compositions of

Fe90−xNixZr10 (x = 0, 5, 10, 15, 20 and 25) were

prepared from pure metals (99.9%) of Fe, Ni and Zr

An arc-melting method was first used to ensure the

homogeneity of the alloys A melt-spinning method

with various quenching rates was then used to fabricate

the ribbon samples The variation of the quenching rate

depended on such factors as the tangential velocity of

the copper wheel, the hole in the quartz crucible, the

injection pressure, etc The thickness (d) of the ribbon

is commonly used to distinguish the quenching rate of

the ribbon In this work, the ribbons with thicknesses

of 15 and 30 µm were investigated The structure of the

samples was examined by using powder X-ray diffraction

(XRD) The magnetic properties of the samples were

characterized by using magnetization measurements

Figure 1 shows XRD patterns of Fe90−xNixZr10

rib-bons with various thicknesses Diffraction peaks

cor-responding to the crystalline phases of α-Fe, FeNi and

NiZr2are observed in these patterns However, the

crys-talline fraction in all the samples is small,i.e., the

amor-phous phase is dominant We can see that the diffraction

peaks of the thinner (d = 15 m) ribbons, especially the

ones with x = 0 - 15, are very weak, which means these

ribbons are almost amorphous The structural phase

fraction strongly influences the magnetic properties of

the alloys as presented below

Thermomagnetization measurements was performed

for Fe90−xNixZr10 ribbons with different thickness

Fig-ure 2 presents reduced thermomagnetization curves for

some typical ribbons The thermomagnetization curves

of the ribbons with d = 30 µm manifest their multi-phase

behaviors These ribbons have a magnetic phase

transi-tion in the temperature range of 250 - 500 K

correspond-ing to the amorphous phase After the first transition,

the magnetization of these ribbons does not decrease to

zero, but maintains values characterizing the crystalline

phase The magnetic transition in the temperature range

of 250 - 500 K is thought to be of an amorphous nature

because the ribbons prepared at a high quenching rate

(their structure is fully amorphous) only have this

transi-tion As for the ribbons prepared at a low queching rate,

their structure is partly crystalline (the lower the

quench-ing rate, the higher the crystalline fraction) The

magne-tization of the ribbon prepared at temperature above 500

Fig 1 XRD patterns of Fe90−xNixZr10ribbons with d = (a) 30 µm and (b) 15 µm.

Fig 2 (Color online) Reduced thermomagnetization curves in a magnetic field for 100 Oe of Fe90−xNixZr10ribbons

with d = 30 µm The inset shows the thermomagnetization

curves in a magnetic field of 10 Oe of Fe90−xNixZr10ribbons

with d = 15 µm.

K is that of a crystalline phase, which has a Curie tem-perature higher than that of an amorphous phase, and its magnitude is directly proportional to the crystalline

Table 1 Influence of Ni concentration on the coercivity (Hc), Curie temperature (T C), maximum entropy change (|∆S m | max), full width at half maximum (FWHM) of the entropy-change peak and refrigerant capacity (RC) of Fe90−xNixZr10ribbons with

d = 15 µm (∆H = 12 kOe).

Ni (%) H c (Oe) T C (K) |∆S m | max(J·kg −1K−1) FWHM (K) RC (J·kg −1)

Fig 3 (Color online) Hysteresis loops at 300 K of

Fe90−xNixZr10 ribbons with d = 15 µm The inset shows

the magnetization at a field of 12 kOe vs Ni concentration in

the samples

fraction; i.e., it depends on the quenching rate The

magnetization is then increased considerably by heating

the ribbons This is due to the overall crystallization

in the ribbons The magnetization of all the ribbons

reaches zero after the last magnetic transition at a

tem-perature of about 960 K As for the ribbons with d =

15 µm, their magnetization is almost zero after the first

magnetic transition This is in agreement with the above

structure analysis These ribbons are almost amorphous

resulting in a single magnetic phase transition Thus,

the quenching rate plays an important role in reducing

the Curie temperature from a high value to a value in

the room temperature region The quenching rate must

be high enough to make the alloys fully amorphous in

the solid state It should be noted that the Curie

tem-perature of the amorphous phase is considerably raised

with increasing Ni concentration in the alloy To the

con-trary, the Curie temperature of Fe90−xMnxZr10 ribbons

is decreased with increasing Mn concentration [5] These

different trends in the variation of the Curie temperature

of the alloy can be understood in terms of the exchange

interaction The exchange interaction of atoms in the

al-loy is enhanced by Ni, but reduced by Mn The effect of

the Ni concentration on the Curie temperature has a

sig-Fig 4 (Color online) Thermomagnetization curves in var-ious magnetic field of Fe90−xNixZr10ribbons with d = 15 µm.

The inset shows the magnetization vs magnetic field at 300

K obtained from virgin magnetization (dir.) and thermomag-netization (ind.) curves

nificant meaning in controlling the working temperature

of the magnetic refrigerants Figure 3 shows the depen-dence of the magnetization on the external field and the

Ni concentration of the ribbons with d = 15 µm We

can see that, the ribbons have a soft magnetic feature and that their magnetization increases with increasing

Ni concentration The results indicate that the addition

of Ni can decrease the coercivity (see Table 1) and in-crease the saturation magnetization of the alloy These two effects of Ni improve its capacity for applications in magnetic refrigeration

According to the obtained results, we selected four samples of Fe90−xNixZr10(x = 0, 5, 10 and 15) ribbons with d = 15 µm to investigate their GMCE These

sam-ples showed a single magnetic phase transition at tem-peratures near room temperature, which is necessary for practical applications of magnetic refrigerants In this

study, we calculate the magnetic entropy change, ∆S m,

based on thermomagnetization data (Fig 4) From the thermomagnetization curves for the samples in var-ious magnetic fields, we can deduce the magnetization

vs magnetic field, M (H), at various temperatures (Fig.

Fig 5 (Color online) Magnetization vs magnetic field at

various temperatures an deduced from the

thermomagnetiza-tion curves of Fe85Ni5Zr10ribbons with d = 15 µm.

5) This derivation was checked by comparing data

(di-rect data) for a virgin magnetization curve with those

(indirect data) deduced from the thermomagnetization

curves (inset of Fig 4) We found that the data

ob-tained from the two different ways agreed The ∆S m

was then determined from the M (H) data by using the

following relation:

∆S m=

H2

H1



∂M

∂T



By using the proposed method to calculate the entropy

change of magnetocaloric materials, we could save

exper-imental time and expense This method is also useful for

avoiding the effect of thermal fluctuations in the

mea-surement systems

Figure 6 presents ∆S m (T ) curves (∆H = 12 kOe) for

the Fe90−xNixZr10 (x = 0, 5, 10 and 15) ribbons with

d = 15 µm The maximum entropy change (|∆S m | max)

of the alloy is nearly unchanged (∼1 J·kg −1K−1 with

∆H = 12 kOe) while the full width at half maximum

(FWHM) of the entropy change peak gradually decreases

(from 92 K to 74 K) with increasing Ni concentration

(see Table 1) The refrigerant capacity (RC) of the

sam-ples, which is defined as the product of the maximum

entropy change (∆S max) and the full width at half

max-imum (FWHM) of the entropy change peak, was also

calculated (see the inset of Fig 6) The RC of the

al-loy first increases and then decreases with increasing Ni

concentration from 0 to 15 at% Nevertheless, a

max-imum RC of about 90 J·kg −1 is achieved at a Ni

con-centration of 5 at% for temperature around room

tem-perature This RC of the Fe90−xNixZr10 alloys is higher

than those of some amorphous and nanocrystalline alloys

such as Finemet (Fe68.5Mo5Si13.5B9Cu1Nb3),

Nanop-erm (Fe83−xCoxZr6B10Cu1, Fe91−xMo8Cu1Bx),

HiT-Fig 6 (Color online) ∆S m (T ) curves (∆H = 12 kOe) of

Fe90−xNixZr10ribbons with d = 15 µm The inset indicates

the refrigerant capacity (RC) vs Ni concentration of the alloy

perm (Fe60−xMnxCo18Nb6B16), and bulk amorphous

al-loys (FexCoyBzCuSi3Al5Ga2P10) [6].

Table 1 present a summary of the influence of the Ni

concentration on the coercivity (H c), Curie temperature (T C), maximum entropy change (|∆S m | max), full width

at half maximum (FWHM) of entropy change peak, re-frigerant capacity (RC) of the Fe90−xNixZr10 (x = 0, 5,

10 and 15) ribbons with d = 15 µm In comparison with

other materials, we can see that the Fe-Ni-Zr alloy is

a good candidate for practical applications in magnetic refrigeration technology

III CONCLUSION

The Curie temperature of the Fe-Ni-Zr alloy can be regulated in the region of room temperature by choos-ing an appropriate quenchchoos-ing rate and Ni concentration The quite high maximum entropy change,|∆S m | max >

1 J·kg −1K−1 for ∆H = 12 kOe, and the wide work-ing range around room temperature, ∆T ∼ 85 K, reveal

potential applications of the rapidly-quenched Fe-Ni-Zr-based alloys in magnetic refrigeration technology

ACKNOWLEDGMENTS

This work was supported by the National Founda-tion for Science and Technology Development (NAFOS-TED) of Vietnam under grant number of 103.02-2011.23 and the Converging Research Center Program funded

by the Ministry of Education, Science and Technology (2012K001431), South Korea A part of the work was

done in the Key Laboratory for Electronic Materials and

Devices, and Laboratory of Magnetism and

Supercon-ductivity, Institute of Materials Science, in Vietnam

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