Synthesis and physical property of triangular lattice antiferromagnet InFe₂O₄

Sagnetic and electrical properties of InFe₂O₄ were investigated. InFe₂O₄ belongs to the RFe₂O ₄ family where R is trivalent cation (R = In, Yb, Lu, Er, or Y). In the rhombohedral crystal structure of this compound, the double layers of FeO₅ bipyramids make two-dimensional triangular lattices and are separated by RO₆ octahedra. Since the numbers of Fe²⁺and Fe³⁺ ions are equal in the triangular lattice, the coexistence of charge and magnetic frustrations is expected. We succeeded in preparing high-quality InFe₂O₄ samples by a solid state reaction from In₂O₃, Fe and Fe₃O₄ in a vacuum sealed tube. A small amount of Fe₃O₄ was magnetically separated. The dielectric constant, magnetic susceptibility, high-field magetization, Mössbauer spectroscopy, and the specific heat data suggested that charge and ferrimagnetic ordering took place simultaneously at 240 K in this compound.