Magnetization of Holmium Iron Garnet at 4.2°K

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Abstract
Magnetic measurements have been made on a spherical single crystal of holmium iron garnet at 4.2°K, in fields of up to 44 kOe. The sample was mounted in such a way that, by rotation about a 〈110〉 direction, any direction lying in the plane perpendicular to the axis of rotation could be brought parallel to the applied field and held there. An extraction method was used for these measurements. In any direction, domain movement is observable only below 6 kOe; above this the magnetization varies linearly: M (H) = M (0)+χH. M (0) has a flat maximum about the direction of easy magnetization 〈111〉. The directions 〈110〉 and 〈100〉 are directions of difficult magnetization where M (0) exhibits very sharp minima. We find that M (0) varies proportionally with the cosine of the angle between the 〈111〉 axis and the direction of the field. This is in conformity with the results of neutron diffraction experiments. The maximum value of M (0) gives a value for the resultant magnetic moment of 13.6 μB per formula unit Fe5Ho3O12. The differential susceptibility in this direction is equal to 0.02 μB/kOe=1.27×10−4/g, and is larger in the other directions. The canted arrangement of the moments of the holmium ions is thus sensitive to the field in this temperature range.

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