Cationic Ordering and Microstructural Effects in the Ferromagnetic Perovskite La0.5Ba0.5CoO3: Impact upon Magnetotransport Properties

TL;DR

This study investigates how cationic ordering and microstructural variations in La0.5Ba0.5CoO3 influence its magnetic and magnetotransport properties, revealing nanoscale ordering effects on coercivity and magnetoresistance.

Contribution

It introduces a third nanoscale-ordered phase of La0.5Ba0.5CoO3 and analyzes its unique magnetic and transport behaviors compared to disordered and fully ordered phases.

Findings

Nanoscale-ordered LaBaCo2O6 is a hard ferromagnet with high coercivity.

All phases show similar Curie temperatures around 174-179 K.

Ordered phase exhibits higher tunnelling magnetoresistance (~15%) at low temperatures.

Abstract

The synthesis and structural study of the stoichiometric perovskite La0.5Ba0.5CoO3 have allowed three forms to be isolated. Besides the disordered La0.5Ba0.5CoO3 and the perfectly ordered layered LaBaCo2O6, a third form called nanoscale-ordered LaBaCo2O6, is obtained. As evidenced by transmission electron microscopy investigations, the latter consists of 112-type 90 degree oriented domains fitted into each other at a nanometer scale which induce large strains and consequently local atomic scale lattice distortions. These three ferromagnetic perovskites exhibit practically the same Tc (174-179 K), but differently from the other phases, the nanoscale-ordered LaBaCo2O6 is a hard ferromagnet, with Hc = 4.2 kOe, due to the strains which may pin domain walls, preventing the reversal of the spins in a magnetic field. The magnetotransport properties of these phases show that all of them exhibit a maximum intrinsic magnetoresistance, close to 6-7 % around Tc under 70 kOe but that the ordered phase exhibits a much higher tunnelling magnetoresistance effect at low temperature of about 15 % against 4 % due to the grain boundary effects.