Field-Induced Transitions in the Hematite Crystal

Magnetization of a single crystal of α-Fe 2 O 3 was measured in a magnetic field up to 80 kOe in the temperature range between 4.2° and 295°K. When the magnetic field was applied parallel to the [111] axis, the field-induced-transitions from the antiferromagnetic to the weak ferromagnetic states were observed below 213°K. From the critical fields thus obtained, the temperature dependence of anisotropy was determined. The anisotropy energy at 4.2°K was found to be -7.2×10 4 erg/gr. When the field was applied perpendicular to the [111] axis, the field-induced transitions from the weak ferromagnetic to the antiferromagnetic state were observed at 236° and 240°K. The field-induced transitions mentioned above are discussed on the basis of Dzyaloshinskii's theory for α-Fe 2 O 3 .