DSpace at VNU: The substitution effect of Cr about large magnetocaloric effect in amorphous Fe-Si-B-Nb-Au ribbons

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Journal of Magnetism and Magnetic Materials 300 (2006) e385–e387
www.elsevier.com/locate/jmmm

The substitution effect of Cr about large magnetocaloric effect in
amorphous Fe–Si–B–Nb–Au ribbons
S.G. Mina, L.G. Ligayb, K.S. Kima,c, S.C. Yua,Ã, N.D. Thod, N. Chaud
a

Department of Physics, Chungbuk Nat’l University, Cheongju, 361-763 Korea
Department of Physics, Nat’l University, of Uzbekistan, Tashkent 700-174 Uzbekistan
c
Basic Science Research Institute, Chungbuk Nat’l University, Cheongju, 361-763, Korea
d
Center for Materials Science, Department of Physics, Hanoi University of Science, 334 Nguyen Trai, Hanoi, Vietnam
b

Available online 16 November 2005

Abstract
The magnetization behaviors have been analyzed for amorphous Fe73.5ÀxCrxSi13.5B9Nb3Au1(x ¼ 0, 3, 5) alloys. An amorphous phase
was formed after quenching by melt spinning with a copper wheel surface speed of 30 m/s. The structure analysis of as-cast was
performed using X-ray diffractometer. The magnetic properties of the ribbons were measured by VSM. The Curie temperature is
decreased from 629 to 491 K with increasing Cr concentration (x ¼ 025). Temperature dependence of the entropy variation DSM was
calculated from the isothermal magnetization. The maximum of DSM was found to appear in the vicinity of the Curie temperature of the
amorphous phase. The DSM value is 1.7, 1.13 and 0.94 J/kg K at x ¼ 0, 3, and 5, respectively.
r 2005 Published by Elsevier B.V.
Keywords: Magnetocaloric effect; Isothermal magnetization; Amorphous ribbon

1. Introduction

The temperature change of a magnetic material,
associated with an external magnetic field change in an
adiabatic process, is defined as the magnetocaloric effect
(MCE). The thermal effect was discovered in 1881 by
Warburg when he applied varying magnetic field to metal
iron [1]. Debye and Giauque explained the nature of MCE
later and suggested achieving an ultralow temperature by
adiabatic demagnetization cooling [2,3]. MCE is intrinsic
later and suggested achieving an ultralow temperature by
adiabatic demagnetization cooling [2,3]. MCE is intrinsic
to magnetic solids and is induced via the coupling of the
magnetic sublattice with the magnetic field, which alters the
magnetic part of the total entropy due to a corresponding
change in the magnetic field. It can be measured and/or
calculated as the adiabatic temperature change DT ad ðT; DHÞ,
or as the isothermal magnetic entropy change DS M ðT; DHÞ
[4–6]. The MCE is a function of both temperature T and the

ÃCorresponding author. Tel.: +82 43 261 2269; fax: +82 43 265 6416.

E-mail address: (S.C. Yu).
0304-8853/$ - see front matter r 2005 Published by Elsevier B.V.
doi:10.1016/j.jmmm.2005.10.125

magnetic field change DH and is usually recorded as a
function of temperature at a constant DH.
Recently, a search for new magnetic materials, which
exhibit a significant change in the magnetic entropy in
response to the change of magnetic field under isothermal
conditions, has become an important task in applied

physics. Traditionally, diluted paramagnetic slats and rare
earth intermetallic compounds that display significant
MCE were considered as attractive materials for cryogenic
applications [4,5].
In our work, magnetization and MCE of
Fe73.5ÀxCrxSi13.5B9Nb3Au1(x ¼ 0, 3, 5) compounds were
investigated. These kind of amorphous materials have
many useful properties that are attractive for application as
magnetic refrigerants.
2. Experiments
The soft magnetic ribbons Fe73.5ÀxCrxSi13.5B9Nb3Au1
(x ¼ 0, 3, 5) alloys have been prepared by rapid quenching
technology on a single copper wheel. The linear speed of
the copper wheel was 30 m/s. The ribbon had the width of
7 mm and the thickness of 16.8 mm. The structure analysis


ARTICLE IN PRESS
S.G. Min et al. / Journal of Magnetism and Magnetic Materials 300 (2006) e385–e387

of ribbons was performed using X-ray diffractometer
Bruker 5005 using Cu-Ka radiation. The thermal transition
was examined by SDT 2960 TA Instrument. The magnetic
properties of the ribbon were measured by VSM.
According to thermodynamic theory, the magnetic
entropy change caused by the variation of the external
magnetic field from 0 to H max is given by

Z H max 
qS

dH.
(1)
DS M ¼
qM T
0
From Maxwell’s thermodynamic relationship:


 
qM
qS
¼
.
qT H
qH T
Eq. (1) can be rewritten as follows:

Z H max 
qM
dH.
DS M ¼
qT H
0

(2)

(3)

Numerical evaluation of the magnetic entropy change
was carried out from formula (3) using isothermal

magnetization measurements at small discrete field and
temperature intervals. DS M can be computed approximately from Eq. (3) by
X M i À M iþ1
jDSM j ¼
DH.
(4)
T iþ1 À T i
i
Thus, the magnetic entropy changes associated with
applied field variations can be calculated from Eq. (4).
3. Results and discussion
It is known that the favorable soft magnetic properties of
Fe-based nanocrystalline alloys come from extremely small
magnetic anisotropy and magnetostriction due to small
grain size. For this purpose, much work has been done on
the Fe-based amorphous alloys by annealing process for
very good soft magnetic properties. Among the nanocrystalline materials, conventional Fe–Nb–Cu–Si–B type (FINEMET) alloys were reported to exhibit excellent soft
magnetic properties with a high saturation magnetization
and a high permeability [6,7]. Especially, appropriate
substitution of Cr and Au in the FINEMET systems
improved coercive force and core loss at high frequency
even in amorphous state [8,9]. For the above reasons, the
devitrification process of the studied alloy is analogous to
that of the usual amorphous Fe–Cr–Si–B–Nb–Au type
materials. In order to gain further insight into the MCE of
the Fe73.5ÀxCrxSi13.5B9Nb3Au1 (x ¼ 0, 3, 5) alloys, we have
carried out magnetization studies.
It takes place in two main stages, as evidenced by the two
well-resolved exothermal peaks in the DSC curve. The first
exotherm corresponds to the appearance of the (Fe,Si)

crystals which remain embedded in the remaining amorphous matrix. The second crystallization process is related
to the formation of boride-type phases and recrystallization phenomena[10,11].

The influence of the presence of Cr on the devitrification
process is an enhancement of the stability of the alloy
against crystallization, as observed in the increase of $40 K
in the peak temperature of the first exothermal maximum.
Fig. 1 shows the temperature dependence of low-field
magnetization for the samples. The Curie temperature, T c
was found to be 629, 545 and 491 K for x ¼ 0, 3 and 5 of
Fe73.5ÀxCrxSi13.5B9Nb3Au1, respectively. With an increase
of the concentration of Cr for Fe73.5ÀxCrxSi13.5B9Nb3Au1
system, the Curie temperature decreases. According to
Franco et al. [11], with increasing Cr concentration,
thermal stability is enhanced and Curie temperature is
reduced, due to the reduce in coupling between the
nanocrystals in amorphous matrix.
Isothermal M2H curves have been measured at various
temperatures in the vicinity of Curie temperature (see the
top panel of Fig. 2). To determine the type of the phase
transition for Fe73.5Si13.5B9Nb3Au1, the measured data for
the M2H isotherms were transferred into H=M vs. M 2
plots and displayed in the bottom panel of Fig. 2.
According to the Banerjee criterion, the negative slope in
H=M vs. M 2 plots means that the ferromagnetic (FM) to
paramagnetic (PM) phase transition is of first order [12].
For the Fe73.5Si13.5B9Nb3Au1, the negative slopes in the
temperature region 626–668 K are clearly seen in the lower
M 2 region, implying that Fe73.5Si13.5B9Nb3Au1 belongs to
the materials displaying a first-order transition.

In evaluating the magnetocaloric properties of the
Fe73.5ÀxCrxSi13.5B9Nb3Au1 (x ¼ 0, 3, 5) samples, the
magnetic entropy change, a function of temperature, and
magnetic field, produced by the variation of the magnetic
field from 0 to H max is calculated by Eq. (4) [13], DS M vs. T
for the all samples, was plotted in Fig. 3. As can be seen in
Fig. 3, with a magnetic field varying from 0 to 1.5 T, the
magnetic entropy change DS M reaches a maximum value of
about 1.7 J/kg K for x ¼ 0 at 629 K, while DS M is about

70
60
Magnetization (emu/g)

e386

50
40
30
20

Fe73.5-xCrxSi13.5B9Nb3Au1

10
0
350

x=0
x=3
x=5

Hdc= 50 Oe

400

450

500
550
Temperature (K)

600

650

Fig. 1. Temperature dependence of the magnetization measured at 50 Oe
for Fe73.5ÀxCrxSi13.5B9Nb3Au1 (x ¼ 0, 3, 5).


ARTICLE IN PRESS
S.G. Min et al. / Journal of Magnetism and Magnetic Materials 300 (2006) e385–e387

574
579
584
589
594
599
602
605
608

611
614
617
620
623
626
629
632
635
638
643
648
653
658
663
668

60

40

20

1.8
1.6

∆ SM J/Kg K

Magnetization (emu/g)

80

H/M (Oe g/emu)

1200

574
579
584
589
594
599
602
605
608
611
614
617
620
623
626
629
1 632
A 635
a 638
643
648
653
658
663

668

Fe73.5-xCrxSi13.5B9Nb3Au1
x=0

1000
800
600
400
200
0
0

1000

2000

3000
4000
M2 (emg/g)2

5000

6000

Fig. 2. Top panel: Isothermal magnetization curves in the vicinity of Curie
temperature for Fe73.5Si13.5B9Nb3Au1. Bottom panel: The H=M vs. M 2
plots for the isotherms of Fe73.5Si13.5B9Nb3Au1.

x=0

x=3
x=5

1.2

∆ H =1.5T

1.0
0.8

0.2
440 460 480 500 520 540 560 580 600 620 640 660 680
Temperature (K)
Fig. 3. Temperature dependence magnetic entropy obtained under a field
change from 0 to 1.5 T, for x ¼ 0, 3, 5 of Fe73.5ÀxCrxSi13.5B9Nb3Au1
(x ¼ 0, 3, 5).

Acknowledgement
This work was supported by Korea science and
Engineering Foundation through the Research Center for
Advanced Magnetic Materials at Chungnam National
University.

References
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[2]
[3]
[4]

1.13, 0.94 J/kg K for x ¼ 3, 5 at 545 and 491 K (the Curie

temperature), respectively.

[5]

4. Conclusion

[7]
[8]

The magnetic properties and entropy changes of
Fe73.5ÀxCrxSi13.5B9Nb3Au1 (x ¼ 0, 3, 5) amorphous alloys
were investigated. The Curie temperature and the maximum value entropy change decreases with increasing Cr
concentration, and the peaks of entropy change appear at
the Curie temperature region. The maximum value of
entropy change decreases with increasing Cr concentration.
Our results show that these amorphous samples are useful
for application as magnetic refrigerants.

1.4

0.4

2000 4000 6000 8000 10000 12000 14000 16000
Magnetic Field (Oe)

1400

Fe73.5-xCrxSi13.5B9Nb3Au1

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e387

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