Parasitic Ferrimagnetism of YFe₂O₄

Abstract

Magnetic properties and electrical conductivity of the YFe₂O₄ single crystal were investigated. It was disclosed that YFe₂O₄ is an antiferromagnet whose Néel point is 205 K, and the spin lies parallel to the hexagonal c axis. Below T_N, the magnetization parallel to the c axis was not proportional to the magnetic field. A large rotational hysteresis was observed at temperatures between 170 and 120 K. Below 140 K, a weak but very hard ferromagnetic moment parallel to the c axis resulted from field cooling. On the basis of these facts, a model of parasitic ferromagnetism, i.e., preferential location of Fe²⁺ and Fe³⁺ ions on each antiferromagnetic sublattice, is proposed. If such a preferential location is caused by the difference of the exchange interaction constant, YFe₂O₄ is the first example of an annealed random spin system.