Refrigerant capacity and direct measurements of the magnetocaloric effect on LaFe11.2Co0.7Si1.1Cx materials
Résumé
In this paper, we report on the magnetic properties and magnetocaloric effect (MCE) in NaZn13-type LaFe11.2Co0.7Si1.1Cx (x = 0.1 and 0.3) close to room temperature. The Landau theory as well as the temperature dependence of magnetization data revealed that LaFe11.2Co0.7Si1.1C0.1 and LaFe11.2Co0.7Si1.1C0.3 exhibit a second-order magnetic transition near their Curie temperature. We have calculated the magnetocaloric effect both in terms of isothermal entropy change and adiabatic temperature change using the magnetization and the direct measurements. Under an external field change from 0 to 5 T, −ΔS is 14.5 J/kg K (TC = 290 K) and 8 J/kg K (TC = 310 K) for x = 0.1 and 0.3, respectively. The calculated refrigerant capacity for a field change in 0-5 T is about 305 and 286 J/kg K, for LaFe11.2Co0.7Si1.1C0.1 and LaFe11.2Co0.7Si1.1C0.3 respectively, which is larger than that of some magnetocaloric materials with a first-order phase transition (Gd5Ge2Si2). ΔTad decreases with increasing C content. It was found to be about 1.5 for x = 0.1 and 1.2 for x = 0.3 under 1.48 T.