Structural, magnetic, and electrical transport properties of half-metallic double perovskite La2CrNiO6 oxides

Abstract

We report on hydrothermal growth of double perovskite La2CrNiO6 (LCNO) powders, which are theoretically predicted to be half-metallic ferrimagnet. Their structural, magnetic, and electrical transport properties are comprehensively studied. The crystal structure of LCNO powders belongs to an orthorhombic crystal structure with Pbnm space group. The saturation magnetization of the LNCO powders was 0.32 μB/f.u. at 5 K (close to the theoretical value of 0.30 μB/f.u. calculated for a disordered system) and the coercive field was 3000 Oe. The negative Curie-Weiss (CW) temperature (θp = −35 K) indicates the predominant antiferromagnetic (AFM) interactions in the powders and ferrimagnetism with magnetic Curie temperature (TC) of 106 K. A spin glass-like behavior was observed in the LNCO powders as cooling the sample from paramagnetic state to the low-temperature ferro/ferrimagnetic state, which is originated from the magnetic interaction competitions via the AFM (Cr4+−O−Cr4+, Ni2+−O−Ni2+ or Ni2+−O−Cr3+) and FM (Ni2+−O−Cr4+ and Ni3+−O−Cr3+) magnetic paths. The observed sharply down deviation from the Curie-Weiss law below 290 K is decreased with the applied magnetic field increased, which leads to Griffiths-like phase in the powders. XPS spectroscopy reveals dual chemical states of Ni ions (Ni2+ and Ni3+) and Cr ions (Cr3+and Cr4+) in the powders, and two kinds of oxygen species exist in the forms of lattice oxygen and adsorbed oxygen. The electrical transport process of the LCNO powders is governed by small polaron variable range hopping mechanism, where the hopping path of localized electrons are provided by the B-site heterovalent metal Ni and Cr ions.