Neutron Diffraction Study of the Magnetic Structures for the Perovskite-Type Mixed Oxides La (Mn, Cr)O3

Abstract

A neutron diffraction study has been made of the magnetic properties of the series of perovskite-like compounds $\mathrm{La}\mathrm{}\left[\right(1-x)\mathrm{}\mathrm{Mn}, x\mathrm{Cr}]{\mathrm{O}}_3$. This series exhibits ferromagnetic and antiferromagnetic properties which depend on the composition of the sample. The antiferromagnetic structure of pure LaMn${\mathrm{O}}_3$ persists only for very small concentrations of ${\mathrm{Cr}}^{+3\mathrm{}}$; the antiferromagnetic structure characteristic of pure LaCr${\mathrm{O}}_3$ is found over a large composition range. For samples of intermediate composition a ferromagnetic moment is observed, the maximum occurring at about 20% ${\mathrm{Cr}}^{+3\mathrm{}}$. In contrast to the mixed oxides $\mathrm{}\left[\right(1-x)\mathrm{}\mathrm{La}, x\mathrm{Ca}]\mathrm{Mn}{\mathrm{O}}_3$ which for certain compositions were truly ferromagnetic, the maximum ferromagnetic moment in this series is very much less than that expected if all the spins were contributing to the moments. A complex ferrimagnetic structure is suggested for the intermediate composition range.