The magnetocrystaline anisotropy of synthetic single crystals of hematite ($\alpha -{\mathrm{Fe}}_2{\mathrm{O}}_3$), both pure and doped with ${\mathrm{Ga}}^{3+}$, ${\mathrm{Al}}^{3+}$, and ${\mathrm{Ti}}^{4+}$, has been measured. The principal anisotropy constant $K_1^{}{}_{}{}^{\prime }$ has been determined below the low-temperature (Morin) transition by spin-flop measurements. An analysis of these data that considers the origins of the anisotropy has permitted the prediction of the transition temperature. Although the transition temperature is a sensitive function of doping, the predicted values are in excellent agreement with those observed experimentally. The magnetocrystalline anisotropy in the basal plane above the transition temperature has been studied with ferromagnetic-resonance techniques. The in-plane anisotropy is observed to be remarkably sensitive to stress but only slightly dependent on doping.

• Received 22 June 1966

DOI:https://doi.org/10.1103/PhysRev.153.632