Magnetization, coercive force, radio frequency, and static susceptibilities were measured near the magnetic orientation phase transition point of the Fe 3 BO 6 crystal. The data exhibit characteristic features of both first and second order transitions, thus indicating the nearly intermediate nature of the ⌫ 2 -⌫ 4 transition in this material.

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A SQUID magnetometer is used to study the behavior of the magnetization of TmFeO3 single crystals along the a and c principal crystallographic axes in the Γ4–Γ24–Γ2 spin reorientation range. The temperature dependences are obtained as the moduli of the magnetization vector M and its turn angle θ in the reorientation range. The results are compared with the same results for ErFeO3. It is shown that even though the experimental dependences |M|(T) and θ(T) are qualitatively different in TmFeO3 and ErFeO3 they can all be convincingly described on the basis of a modified mean-field theory previously proposed by the authors. Since the theoretical analysis does not include any parameters which are not known from experiment, the agreement between theory and experiment confirms that the model proposed for describing Γ4–Γ24–Γ2 phase transitions in orthoferrites is a general model. Dedicated to E. S. Borovik—Scientist and Humanitarian “Who can say what influence the silent presence of one person has on another?” Walter De la Mar

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Comparative analysis of the results of measurements of soft magnetic resonant modes in weak ferromagnets with different temperatures of spontaneous reorientation is carried out. It is shown that the longitudinal oscillations of magnetization make a contribution to the energy gap even in zero magnetic field (in the case of spontaneous reorientation) and increases with increasing temperature alone.