J. Phys. IV France 115 (2004) 105
DOI: 10.1051/jp4:2004115013

Magnetocaloric and shape-memory effects in Ni-Mn-Ga ferro-magnetic alloys

J. Marcos¹, L. Mañosa¹, A. Planes¹, F. Casanova², X. Batlle², A. Labarta² and B. Matínez<sup>3

1</sup>  Departament d'Estructura i Constituents de la Matèria, Facultat de Física, Universitat de Barcelona, Diagonal 647, 08028 Barcelona, Catalonia, Spain
²  Departament de Física Fonamental, Facultat de Física, Universitat de Barcelona, Diagonal 647, 08028 Barcelona, Spain
³  Institut de Ciència de Materials de Barcelona, CSIC, 080193 Bellaterra, Spain

Abstract
We show that an isothermal entropy change can be induced in Ni-Mn-Ga by the application of moderate magnetic fields. This magnetocaloric effect is originated by two different contributions: (i) the magnetostructural coupling which takes place at the length scale of martensitic variants and magnetic domains (mesoscopic coupling) and (ii) the microscopic spin-phonon coupling. The first contribution is intimately related to the magnetic shape-memory property and controls the magnetocaloric effect for small inducing fields. The latter contribution is dominant for high fields.

© EDP Sciences 2004