Mössbauer Study of the Magnetic Field Dependence of the Spin Flop inα−Fe2O3near the Morin Transition

It is found that an external magnetic field applied in the basal (111) plane of a single crystal of $\alpha -{\mathrm{Fe}}_2{\mathrm{O}}_3$ causes the Morin transition temperature to be depressed. The detection of the transition was accomplished by observing the appearance of one of the two $\Delta m=0\mathrm{}$ lines in the Mössbauer spectrum of ${\mathrm{Fe}}^{57}$ as the crystal warmed through the transition region. From the measurements, the temperature dependence of the antiferromagnetic anisotropy energy can be determined and compared with that predicted on the basis of the Dzyaloshinsky treatment of the weak ferromagnetism in $\alpha -{\mathrm{Fe}}_2{\mathrm{O}}_3$.