Magnetoresistance of the spin-state-transition compound La_1−xSr_xCoO₃

Abstract

We have investigated the magnetoresistance (MR) of the perovskite oxide La_1−xSr_xCoO₃ for 0≤x≤0.4 which shows a spin-state transition from low-spin Co^III to high-spin Co³⁺ as a function of temperature. In the metallic compositions (x≤0.25) appreciable MR occurs only near the ferromagnetic Curie temperature. For the most metallic composition x=0.4, there is a small positive contribution to the MR near the T_c. In the insulating samples (x≤0.2) the MR shows a large hysteresis which depends on the temperature. The value of the MR is negative and large in the insulating compositions and shows a maximum near the temperature where magnetic studies showed a spin-glass-like transition. We also find a strong role of the spin-state transition of the Co³⁺ ions in the electronic transport leading to a characteristic behavior of the MR in the Co³⁺-rich insulating samples.