Crystal structure and physical properties of Cr and Mn oxides with 3d3 electronic configuration and a K2NiF4-type structure

Abstract

YSrCrO₄ is first synthesized and found to be a hettotype of the K₂NiF₄ structure, although the combination of Y and Sr ions in K₂NiF₄-type oxides is very rare. The space group of the compound is determined to be orthorhombic Pccn by the electron diffraction and the powder X-ray diffraction. Magnetic and dielectric properties of the compound, together with LaSrCrO₄, YCaCrO₄ and A₂MnO₄ (A = Sr and Ca), are investigated. YSrCrO₄ shows two-dimensional (2D) spin correlations and a canted antiferromagnetic (AF) ordering. With increasing distortion of the crystal structure, 2D spin correlations and the AF transition temperature decrease, while spontaneous magnetization increases. From the multi-frequency electron spin resonance (ESR) measurements, the g-values of the paramagnetic state are estimated to be 1.976, 1.978 and 1.976 for YSrCrO₄, LaSrCrO₄ and YCaCrO₄, respectively. Evidence of AF ordering of the Cr oxides is obtained microscopically from ESR. The dielectric measurements suggest the existence of in-gap states, while no magneto-dielectric coupling was observed in the above compounds.