Magnetocrystalline Anisotropy of Gallium Iron Oxide

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Abstract
Magnetocrystalline anisotropy measurements have been made on a sample1 of ferromagnetic and piezo‐electric Ga2−xFexO3 (x being near unity) using a torque method. Torque curves in the a‐c plane on an x‐ray oriented single crystal indicate a large uniaxial anisotropy of the form E = K sin2θ, where θ is the angle between Ms and the preferred (c) axis. As the anisotropy field (2K/Ms) is larger than the external field presently available (11 kOe), the anisotropy values were obtained from measurements in which the angle between the external field and the c direction was small. The results obtained with this method show, for example, that the ``effective'' anisotropy field at 77°K is about 40 kOe. This directly measured value is to be compared with the values of 300 kOe and 16 to 23 kOe deduced from energy gap2 and susceptibility3 measurements, respectively. The small‐angle measurements also yield magnetization values which are in substantial agreement with those previously reported. Although exact theoretical treatment must await determination of its crystallographic and magnetic structure, it is believed that the observed anisotropy can be explained by the presence of strong crystal fields at the Fe3+ sites.

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