Magnetic Properties ofMn3O4and the Canted Spin Problem

The magnetic properties of single crystals of hausmannite (${\mathrm{Mn}}_3$ ${\mathrm{O}}_4$) have been investigated between 4.2°K and the ferrimagnetic Curie point at 41.9°K. The $c$ axis was found to be the hard direction of magnetization and the $c$ plane was found to possess considerable anisotropy, with respective anisotropy fields of about ${10}^5$ oe and ${10}^4$ oe. These anisotropy energies decreased slowly with increasing temperature, whereas the coercive force at 15°K was about an order of magnitude less than at 4.2°K. The spontaneous magnetization is 1.85 ${\mathrm{\mu }}_{\mathit{B}}$/molecule, which agrees with previous polycrystalline values when the observed anisotropies are taken into account. However, several of the observed properties of hausmannite disagree, some quantitatively and others qualitatively, with calculations based on the Yafet-Kittel theory. It is concluded that the concept of canted spins is essentially correct, but that the specific Yafet-Kittel model involves oversimplifications which limit its applicability.