MAGNETIC FIELD INDUCED ANTIFERROMAGNETIC TO WEAKFERROMAGNETIC TRANSITIONS IN HEMATITE

The Antiferromagnetic-Weakferromagnetic, AF - WF, phase transition in hematite was studied as a function of temperature and field, by measuring the angular dependence of the magnetization curve to fields as high as 10K Gauss at temperatures close to the Morin transition. It Is found that the AF - WF phase boundary Is adequately described by the theoretical expression H(perpendicular to) = a - x(perpendicular to) - x(N)/2 sigma H(N) a where H(parallel to), X(parallel to) and H(perpendicular to), X(perpendicular to) are the field and susceptibility along and perpendicular to the C axis, sigma is the weak ferromagnetic moment and "a", a temperature dependent parameter.