Magnetic and magnetothermal properties of La1-xNdxFe11.5Al1.5 compounds

In this paper, we report the structural, magnetic, and magnetocaloric effect (MCE) of La1-xNdxFe11.5Al1.5 (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 (Delta S-M) using the magnetization isotherms obtained at temperatures close to the transition temperature. The maximum values of Delta S-M 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 J/kg K for x=0.1 and 470 J/kg K for x=0.2. (C) 2008 American Institute of Physics.