Temperature-induced magnetization reversal in a YVO3 single crystal

The total energy of a magnet in a magnetic field is lowest when the magneti c moment is aligned parallel to the magnetic field. Once aligned, the magne tic moment can be reversed by applying a sufficiently large field in the op posite direction. These properties form the basis of most magnetic recordin g and storage devices. But the phenomenon of magnetization reversal in resp onse to a change in temperature tin a small magnetic field) is rarer. This effect occurs in some ferrimagnetic materials consisting of two or more typ es of antiferromagnetically ordered magnetic ions', and forms the operation al basis of ferrimagnetic insulators. Here we report the observation of mul tiple temperature-induced magnetization reversals in YVO3. The net magnetic moment is caused by a tilting of the antiferromagnetically aligned moments of (crystallographically identical) V3+ ions, due to orthorhombic distorti on in the crystal structure. We observe an abrupt switching at 77 K associa ted with a first-order structural phase transition, and a gradual reversal at similar to 95 K without an accompanying structural change. The magnetiza tion always reverses if the crystal is cooled or warmed through these two t emperatures in modest fields. We propose a possible mechanism involving a c hange in orbital ordering which may be generic to a broad class of transiti on metal oxides.