Universal behavior of magnetocaloric effect in a layered perovskite La1.2Sr1.8Mn2O7 single crystal

In this paper, we present a detailed analysis on temperature and magnetic field dependences of the magnetic entropy change (Delta Sm) near the ferromagnetic (FM)-paramagnetic (PM) phase transition of a La1.2Sr1.8Mn2O7 single crystal. Experimental results reveal the material exhibiting a FM-PM phase transition at T-C=85 K, and belongs to a second-order phase transition (SOPT). Around T-C, -Delta S-m reaches the maximum value (vertical bar Delta S-max vertical bar), which increases with increasing an applied magnetic field change, Delta H. The vertical bar Delta S-max vertical bar values found are about 0.93, 1.73, 2.38, 2.91, and 3.331 kg(-1) K-1 for Delta H=10, 20, 30, 40, and 50 kOe, respectively. However, the peak position of the -Delta S-m(T) curves is effectively shifted to higher temperatures when Delta H increases. Additionally, the Delta S-m(T) curves measured at different Delta H values do not collapse into a universal curve when they are normalized to their respective Delta S-max value, and Prod. Type: rescaled the temperature axis with theta(1) = (T T-C)/(T-r, T-C) for a reference temperature T-r > T-C or T-r < T-C. Nevertheless, they can be collapsed into a unique curve in the whole temperature range if using two separated reference temperatures, T-r1 and T-r2, with theta(2) = (T - T-C)/(T-r1-T-C) for T <= T-C and theta(2) = (T - T-C) /(T-r2 - T-C) for T > T-C. (C) 2015 Elsevier B.V. All rights reserved.