Crystal Structure, Magnetic and Electrical Properties of Half-Doped Chromium Manganite La0.5Sr0.5Mn0.5Cr0.5O3

Abstract

Polycrystalline sample La0.5Sr0.5Mn0.5Cr0.5O3 (LSMCO) was prepared by a conventional solid-state reaction method in the air, and its structure was determined by Rietveld refinement using consistent resolution time-of-flight X-ray diffraction. Different structural models have been used for analysis of X-ray diffraction data recorded at room temperature, but the best fits have been found using a mixture of rhombohedral and an orthorhombic structural phases (42(1)%/57(1)%). The rhombohedral, centro-symmetric space group R $$ \overline{3} $$ c $$ \left(\mathrm{No}.167,a\approx \sqrt{2}{a}_p,c\approx 2\sqrt{3}{a}_p,Z=6\right) $$ with octahedral tilting scheme a−a−a− leading to a three identical out-of-phase tilt angle of (Mn/Cr)-O6 octahedron along three perovskite main directions: x, y, and z-axes. The orthorhombic space group Pbnm $$ \left(\mathrm{No}.62,a\approx b\approx \sqrt{2}{a}_p,c\approx 2{a}_p,Z=4\right) $$ with octahedral tilting scheme a−a−c+, leads to an anti-phase tilts of the same magnitude about [100] and [010] directions of the elementary specimen cell and in-phase tilt of different magnitude about the [001] direction. At low temperature 10 K, Rietveld refinement of powder diffraction data revealed that the crystal structure of sample is distorted with a single orthorhombic symmetry (space group Pbnm). Magnetic measurements indicate that our investigated sample exhibits an overall anti-ferromagnetic behavior mainly attributed to the frustration induced by both competing AFM Cr3+-O-Cr3+, Mn4+-O-Mn4+ networks, and the mixed one Mn4+-O-Cr3+exchange magnetic interactions. The temperature dependence of the resistivity measured under zero field shows a semi-conducting behavior in the whole temperature range, which probably could be described by the adiabatic small polaron hoping model with relatively high polaron activation energy.