Forming a ferrimagnetic-like structure in the PbMn1−xFexBO4 (x≈0.1) single crystal upon partial substitution

Abstract

The PbMn1−xFexBO4 (x≈0.1) orthoborate single crystals have been grown for the first time by spontaneous crystallization and their magnetic and resonance properties and specific heat have been examined. It has been established that partial substitution of iron ions for manganese ones leads to an increase in the Curie temperature to 34.2 K from its value of 30.3 K in the unsubstituted crystal, enhances the magnetic anisotropy, and reduces the saturation magnetization. The magnetization drop is explained in the framework of the model of a ferrimagnetic-like structure, in which the magnetic moments of iron and manganese ions form ferromagnetic subsystems coupled by the antiferromagnetic exchange. It has been found that under magnetization along the rhombic b axis the magnetic moments switch stepwise to the magnetic field direction in a certain critical field. The spin-reorientation transition is the first-order one. This feature of the crystal magnetization does not allow the experimental ferromagnetic resonance frequency-field dependence for the rhombic b axis to be described using the calculation for a simple rhombic ferromagnet. It has been established that the increase in the magnetic anisotropy of the crystal upon substitution leads to an increase in the energy gap in the ferromagnetic resonance spectrum to 121.5 GHz at T=4.2 K.