Normal and inverse magnetocaloric effects in ferromagnetic Pr _0.58 Sr _0.42 MnO₃

We report magnetization, magnetic entropy change (ΔS _m ), and its correlation with magnetoresistance (MR) in Pr _0.58 Sr _0.42 MnO _3. It is shown that the magnetization upon field-cooling shows a steplike decrease at T _S 134 K much below the ferromagnetic transition (T _C 300 K). While the low temperature transition is first-order, the high temperature transition is second-order as suggested by the hysteresis behavior in magnetization. In a magnetic field range accessible with an electromagnet, the magnetic entropy decreases at T _C (ΔS _m -2.33 J/kg K with a refrigeration capacity of 65.88 J/kg for a magnetic field change of ΔH 2 T) whereas it increases at T _S (ΔS _m 0.7 J/kg K) upon magnetization. The unusual inverse magnetocaloric effect found at T _S within ferromagnetic state is ascribed to orthorhombic to monoclinic structural transition. We show that ΔS _m versus T curves under different magnetic fields can be collapsed into a single master curve using a scaling method. Importantly, we find that negative MR increases linearly with -ΔS _m in the paramagnetic state at all magnetic fields above T _C and at higher magnetic fields below T _C . Such a close correlation between the magnetoresistance and the magnetic entropy change can be exploited to design efficient magnetocaloric materials.