Magnetic and magnetothermal properties of La_1-x Nd_x Fe_11.5 Al_1.5 compounds

In this paper, we report the structural, magnetic, and magnetocaloric effect (MCE) of La1-x Ndx Fe11.5 Al1.5 (x=0.1,0.2) compounds. Temperature dependence of magnetization data shows that with Nd substitution, the nature of magnetic transition changes from second order transition to multiple first order transition. This observation is confirmed by the thermodynamic analysis using the Landau theory of phase transitions. The MCE has been calculated in terms of the isothermal magnetic entropy change (Δ SM) using the magnetization isotherms obtained at temperatures close to the transition temperature. The maximum values of Δ SM are found to be 5.4 and 4.6 J kg-1 K-1 of x=0.1 and x=0.2, respectively, for a field change of 50 kOe, whereas the value for the undoped compound is about 3 J kg-1 K-1. The refrigerant capacity has been calculated to be 544 Jkg K for x=0.1 and 470 Jkg K for x=0.2.