Anomalous Nernst Effect and Giant Magnetostriction in Microwave-Synthesized La0.5Sr0.5CoO3

Abstract

The anomalous Nernst effect (ANE) is the generation of a thermoelectric voltage transverse to the imposed temperature gradient and applied magnetic field in a ferromagnet. This effect enables magnetic metals and alloys to be exploited for heat to electrical energy conversion. Available reports on the ANE in perovskite oxides are very few compared to those on metallic alloys. Here, we report two independent phenomena, ANE and magnetostriction, in the perovskite oxide La0.5Sr0.5CoO3 synthesized by microwave irradiation. La0.5Sr0.5CoO3 is metallic and ferromagnetic below TC = 247 K with electrons as the majority charge carriers. Magnetic field dependence of the Nernst coefficient (Sxy) at a fixed temperature below TC resembles magnetization. The anomalous contribution to Sxy shows a maximum value of ∼0.21 μV/K at 180 K for H = 50 kOe. Analysis of the data indicates that the mechanism of the ANE in this sample is skew scattering in a bad metallic regime. The magnetostriction has a positive sign, that is, the length of the sample elongates along the field direction, and the fractional change in the length is 500 ppm in a magnetic field of 50 kOe for T ≤ 40 K, which is a giant value among 3d perovskite oxides. It is suggested that in addition to field-induced spin–orbit coupling, structural changes also contribute to the observed giant magnetostriction in this compound. The coexistence of both the ANE and the giant magnetostriction in a single material is interesting for thermal energy harvesting and actuator applications.