Normal and inverse magnetocaloric effects in ferromagnetic Pr0.58Sr0.42MnO3

We report magnetization, magnetic entropy change (Delta S-m), and its correlation with magnetoresistance (MR) in Pr0.58Sr0.42MnO3. It is shown that the magnetization upon field-cooling shows a steplike decrease at T-S = 134K 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 (Delta S-m = -2.33 J/kg K with a refrigeration capacity of 65.88 J/kg for a magnetic field change of Delta H = 2T) whereas it increases at T-S (Delta S-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 Delta S-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 -Delta S-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. (C) 2013 American Institute of Physics.