Magnetic and structural phase diagram of the solid solutionLaCoxMn1−xO3

Abstract

We present a structural and magnetic phase diagram of the solid solution ${\text{LaCo}}_{x}{\text{Mn}}_{1\ensuremath{-}x}{\text{O}}_{3}$. We show by neutron diffraction that the monoclinic structure previously observed for the elpasolite form ${\text{La}}_{2}{\text{CoMnO}}_{6}$ (${\text{LaCo}}_{0.5}{\text{Mn}}_{0.5}{\text{O}}_{3}$) is also observed for another member of the solid solution $x\phantom{\rule{0.28em}{0ex}}=\phantom{\rule{0.28em}{0ex}}0.35$. We also present the transition temperatures for the orthorhombic/monoclinic structures of the series to the rhombohedral structure and determine the expected transition temperatures from rhombohedral to cubic symmetry. We present the magnetic structures as determined by neutron diffraction for materials with lower cobalt content and provide evidence, including ac and dc susceptibility measurements, for the possible glassy nature of the magnetism in the cobalt-rich materials in the series. Based on high-resolution neutron diffraction, we also suggest that there is a limit to the ${\text{LaCo}}_{x}{\text{Mn}}_{1\ensuremath{-}x}{\text{O}}_{3}$ solid solution at $x=0.85$. Finally we present a possible, previously unreported, low-temperature monoclinic structure for the sample ${\text{LaCo}}_{0.75}{\text{Mn}}_{0.25}{\text{O}}_{3}$.