Studies of magnetic entropy change and phase transitions in SrRu1−xMnxO3 perovskite

Abstract

This paper reports a systematical investigation on the role of magnetic phase transitions on magnetocaloric effect in polycrystalline SrRu1−xMnxO3 (0⩽x⩽0.72), combining with the temperature dependent magnetization measurement by a superconducting quantum interference device. Mn substitution drives the magnetic phase transition from ferromagnetic state to antiferromagnetic state via a short-range magnetic order. The magnetic entropy change (ΔSM) presents negative values and a maximum at Curie temperature TC and/or spin freezing temperature Tf for 0⩽x⩽0.27, which is due to the contribution of the spin ordering induced by magnetic field. In addition, we also observe positive magnetic entropy changes (ΔSP) at Néel temperature TN for high Mn concentration (x⩾0.41) as the charge ordering is negligible. Since the magnetization is insensitive to external field in the vicinity of TN, the positive magnetic entropy change is considered to stem from the dramatic temperature dependence of the magnetization.