Normal and inverse magnetocaloric effects in ferromagnetic Pr 0.58Sr0.42MnO3

Abstract

We report magnetization, magnetic entropy change (ΔSm), and its correlation with magnetoresistance (MR) in Pr0.58Sr 0.42MnO3. It is shown that the magnetization upon field-cooling shows a steplike decrease at TS 134 K much below the ferromagnetic transition (TC 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 (ΔSm -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 TS (ΔSm 0.7 J/kg K) upon magnetization. The unusual inverse magnetocaloric effect found at TS within ferromagnetic state is ascribed to orthorhombic to monoclinic structural transition. We show that ΔSm 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 -ΔSm in the paramagnetic state at all magnetic fields above TC and at higher magnetic fields below TC. Such a close correlation between the magnetoresistance and the magnetic entropy change can be exploited to design efficient magnetocaloric materials. © 2013 American Institute of Physics.