Magnetic entropy change in rare earth intermetallic
compound GdNi and its melt-spun ribbon
R. Rajivgandhi1, R. Nirmala1*, J. Arout Chelvane2, S. Quezado3 and S. K. Malik3
1
Department of Physics, Indian Institute of Technology Madras, Chennai 600 036, India
2
Defence Metallurgical Research Laboratory, Hyderabad 500 058, India
3
DTFE, UFRN, Natal, 59072-970, Brazil
*Corresponding author’s e-mail: nirmala@iitm.ac.in
Absract
Magnetic properties of intermetallic compound
GdNi in its bulk polycrystalline and melt-spun ribbon forms
have been studied. These samples order ferromagnetically at
~ 69 K and 75 K (TC) respectively. Magnetocaloric effect is
calculated in terms of isothermal magnetic entropy change
and the maximum values ∆Smmax are -31.2 J/kg-K and -28.7
J/kg-K, respectively for the bulk and ribbon samples for a
140 kOe field change.
Keywords: Magnetocaloric effect, rare earth intermetallic
compounds
increasing magnetization in ribbon sample compared to
that in bulk sample.
1.Introduction
Rare earth intermetallic compounds, RNi (R- rare
earth metals) stabilize either in orthorhombic CrB type
structure (for R= La to Tb) with space group Cmcm (No.
63) or in orthorhombic FeB type structure (for R= Dy to
Lu and Y) with space group Pnma (No. 62) [1, 2]. It is
found that Ni is non-magnetic in these compounds [1]. In
this work, magnetic properties of polycrystalline GdNi, in
its as prepared (bulk) and melt-spun ribbon forms are
studied.
Fig. 1 M vs T of GdNi bulk and ribbon samples in 5 kOe
field
2. Experimental details
Bulk GdNi has been prepared by arc melting the
stoichiometric amounts of high pure constituent elements
in argon atmosphere and then annealed at 1173 K for 12 h.
About 2 mm wide, 50 micron thick ribbon has been
prepared by rapidly solidifying the molten GdNi in meltspinning process. Crystal structure and stoichiometry were
confirmed by room temperature powder X-ray diffraction
and energy dispersive X-ray analysis.
Magnetic
measurements have been done by using PPMS (Quantum
Design, USA) from 2 to 300 K in fields up to 140kOe.
Fig. 2 Isothermal Magnetic entropy change vs T for GdNi
(a) bulk and (b) ribbon samples for various field changes
4. Conclusions
GdNi exhibits considerably large magnetocaloric
effect near TC in both bulk and ribbon forms.
References
[1]R. E. Walline and W. E. Wallace, Magnetic and
structural characteristics of lanthanide-nickel compounds,
J.Chem. Phys. 41 (1964), pp. 1587-1591.
Results and discussion
[2] K. H. J. Buschow, and Ed. E.P Wohlfarth, Handbook
Mangetic and magnetocaloric properties of GdNi
of magnetic materials, Volume 1, NorthHolland
compound in bulk and ribbon forms are listed in Table.1.
publishing company, North Holland, 1980.
Both order ferromagnetically but the T C of ribbon is
[3] Pramod Kumar, K. G. Suresh, A. K. Nigam and O.
relatively higher (Fig.1) and correspondingly a broadening
Gutfleisch, Large reversible magnetocaloric effect in
in magnetic entropy change vs T graph is observed in this
RNicompounds, J. Phys. D: Appl. Phys. 41(2008), pp.
sample (Fig.2a and b) and it may be due to a slowly
245006-1-5.
Table.1 Magnetic and magnetocaloric properties of GdNi compound in bulk and ribbon forms
Compound
GdNi Bulk
GdNi Ribbon
TC
(K)
69
69, 71-73
76
θP
(K)
84
77
85
µeff
(µB/F.U)
8.3
7.8, 8.1-8.2
8.6
gJ
(µB/F.U)
7
7
7
µS
(µB/F.U)
7.4
7.4, 7.2-7.4
7.9
-∆Smmax (J/kg-K)
∆H = 50 kOe
∆H = 140 kOe
17.3
31.2
16.2
-15.2
28.7
Ref.
This work
[3], [2]
This work