Antiferromagnetic domain boundary as a line for nucleation of a weakly ferromagnetic phase from the antiferromagnetic one in dysprosium orthoferrite

We have studied the nucleation of a weakly ferromagnetic phase from an antiferromagnetic domain boundary near the Γ14 → Γ14 first order phase transition in dysprosium orthoferrite in a magnetic field H parallel to the c axis of the crystal. We calculate the variation of the orientation of the antiferromagnetism vector 1 in the domain wall for various values of the magnetic field strength and the field dependence of the energy density σ and of the thickness δ of the antiferromagnetic domain boundaries. It is shown that as H increases the central portion of the domain boundary widens and becomes a domain of a weakly ferromagnetic phase at the transition field. The formation of weakly ferromagnetic domains from antiferromagnetic domain boundaries has been visually observed in a field H ‖ c in DyFeO3 plates cut perpendicular to the c axis. From the period of the domain structure of the magnetic intermediate state we obtain the value of the energy density in the domain wall between domains in the antiferromagnetic and weakly ferromagnetic phases. The values obtained for a are in good agreement with calculated ones.

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