Magnetocaloric properties of rapidly solidified Ni 51.1 Mn 31.2 In 17.7 Heusler alloy ribbons
- PDF / 277,916 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 14 Downloads / 181 Views
1200-G07-05
Magnetocaloric properties of rapidly solidified Ni51.1Mn31.2In17.7 Heusler alloy ribbons J.L. Sánchez Llamazares1, B. Hernando1, V.M. Prida1, C. García2, C.A. Ross2 1 Departamento de Física, Facultad de Ciencias, Universidad de Oviedo, Calvo Sotelo s/n, 33007 Oviedo, Spain. 2 Dept. Material Science and Engineering, MIT, 77 Massachusetts Ave., Cambridge, Massachusetts 02139, USA.
ABSTRACT Magnetic entropy change and refrigerant capacity have been determined for a field change of 20 kOe around the second-order magnetic transition of austenite in as-quenched Ni51.1Mn31.2In17.7 alloy ribbons produced by melt spinning technique. Samples crystallize in a single-phase austenite with the highly ordered L21-type crystal structure and a Curie temperature of 275 K. The material shows a maximum magnetic entropy change of ∆SMmax= - 1.7 Jkg-1K-1, an useful working temperature range of 78 K (δTFWHM) and a refrigerant capacity of RC=132 Jkg-1 (RC= │∆SMmax│ x δTFWHM). The considerable RC value obtained together with the fabrication via a single-step process make austenitic Ni-Mn-In ribbons of potential interest as magnetic refrigerants for room temperature magnetic refrigeration.
INTRODUCTION A key issue in the development of room temperature magnetic refrigeration technology is the finding of cheap magnetic materials exhibiting a large enough refrigerant capacity RC for a magnetic field change ∆H below 20 kOe over a broad temperature span around room temperature (20 kOe is the static magnetic field that can be currently generated without energy cost using Nd-Fe-B permanent magnet assemblies). Looking to this goal the magnetocaloric properties of long list of material families showing first-order structural transitions and secondorder magnetic transitions have been evaluated [1,2]. This comprises rare earth-transition metal compounds, transition metal-based alloys, magnetic oxides, and nanocomposites. Among them ferromagnetic shape memory Heusler alloys in the ternary system Ni-Mn-X with X= Sn, In, Sb, have been recently the focus of great interest worldwide. These alloys fulfil the requisite of being relatively cheap with respect to metallic Gadolinium and rare-earth based alloys. On the other hand, they usually exhibit inverse MCE associated to the first-order structural martensitic phase transition and conventional magnetocaloric effect (MCE) around the second-order magnetic transition of ferromagnetic austenite (AST) (i.e. positive and negative magnetic entropy change ∆SM, respectively). In the alloy systems Ni-Mn-Sn [3] and Ni-Mn-In [4-7] some compositions exhibit large or even giant inverse MCE in a temperature interval ranging from 200 K to 330 K. Unfortunately, the temperature region where a large inverse MCE is obtained is usually narrow (i.e. the full width at half maximum of the temperature dependence of the magnetic entropy change ∆SM (T) is not large) and, in addition, large hysteresis losses result from the field-induced reverse martensitic transformation and these two factors diminish the refrigerant ca
Data Loading...
