Effect of Fe Substitution on Structural and Magnetic Properties of NiCr₂O₄

Abstract

At room temperature, the normal oxide spinel NiCr2O4 is tetragonally distorted and crystallizes in the I41/amd space group due to cooperative Jahn-Teller ordering driven by the orbital degeneracy of tetrahedral Ni 2 . The ferrimagnetic Curie temperature (TCq for NiCr2O4 is 74 K. The magnetic moments of NiCr2O4 are composed of a ferrimagnetic (longitudinal) and an antiferromagnetic (transverse) component. Exchange interaction between the magnetic cations influences the overall magnetic properties of the compound. Present work focuses on the modification of structural and magnetic properties upon substituting Fe at Cr site in NiCr2O4 with the motivation of changing the magnetic exchange interaction. In order to do so, single phase Ni(Cr0.5Fe0.5q2O4 samples were prepared by co-precipitation techniques, while controlling the pH of precipitation. Upon Fe substitution, crystal structure was not affected much contrary to the earlier reports. In order to determine the oxidation state of each elements X-ray photoelectron spectroscopy (XPS) was performed. TC was found to increase dramatically above 300 K, confirmed both from temperature and field dependent dc-magnetization studies.