Compositional dependence of the magnetocaloric effect in La_1−xCa_xMnO₃ (0⩽x⩽0.52)

A detailed investigation of the thermodynamic properties of La_1−xCa_xMnO₃ (0⩽x⩽0.52) for possible applications in magnetic refrigeration is presented. The adiabatic magnetic entropy change ∣ΔS∣ is determined for a 2 Tesla change in magnetic field using magnetization measurements. A broad double peak behavior as a function of x is observed with maximum absolute values ∣ΔS∣_max near 5.5 J∕kg K for x≈0.28. The largest ∣ΔS∣_max values do not coincide with the maximum value of the ferromagnetic transition temperature T_c. The relatively large adiabatic magnetic entropy change is moderated by a large heat capacity, which leads to a modest adiabatic temperature change of about 2 K for the x=0.28 specimen. The largest contribution to ∣ΔS∣_max occurs for magnetic field changes in the range 0⩽H⩽2 Tesla; increasing the magnetic field range to 3 Tesla only increases ∣ΔS∣_max by about 20%.