Analysis and modeling of magnetocaloric effect near magnetic phase transition temperature

Mohamed Balli , F. Allab (1) , Cédric Dupuis (1) , Daniel Fruchart (2) , Damien Gignoux , Afef Kedous-Lebouc (1) , J. M. Fournier (1) , J. P. Yonnet (1)

1 G2ELab - Laboratoire de Génie Electrique de Grenoble
2 NEEL - MNM - Micro et NanoMagnétisme

Magnetocaloric behavior of gadolinium near room temperature can be correctly described by the Weiss molecular field theory especially in the paramagnetic state. In this paper, this approach is generalized for binary rare earth alloys which present as Gd a second order phase transition. The magnetic entropy variation can be calculated as a function of the temperature and the applied field. This model was tested on a laboratory synthesized samples of Gd-Tb. The agreement between calculations and experiments shows that this model can be easily used for these alloys in order to optimize their composition and adjust their Curie temperatures. For first order transition materials, the observed magnetocaloric effect enhancement can be explained by magnetoelastic effects which are due to the spontaneous crystal deformation and the structure transformation. A model based on the phenomenological approach of Bean Rodbell is developed to describe such a behavior. It highlights the link between the nature of magnetic transition and the magnetocaloric effect. It can be identified by only two parameters: T 0 the Curie temperature without deformation and η an order parameter which characterizes the transition nature. In this paper we apply this model to describe the giant magnetocaloric effect exhibited by the new Mn 1-x (Ti 0.5 V 0.5) x As materials.

Mots clés: matériaux magnétocaloriques; réfrigération magnétique; effect magnétocalorique

Domaines: Matière Condensée [cond-mat]

Mohamed Balli, F. Allab, Cédric Dupuis, Daniel Fruchart, Damien Gignoux, et al.. Analysis and modeling of magnetocaloric effect near magnetic phase transition temperature. Second IIF-IIR International Conference on Magnetic Refrigeration at Room Temperature, Apr 2007, Portoroz, Slovenia. ⟨hal-01185995⟩