Spectroscopic and magnetooptical investigations of spin-reorientation phase transition in TbFe₃(BO₃)₄

Spectroscopic and magnetooptical investigations of magnetic field induced spin-reorientation phase transition in antiferromagnetic terbium ferroborate TbFe₃(BO₃)₄ were performed. It is found that in the vicinity of the phase transition there appears a magnetic intermediate state with periodic alternation of initial phase domains and domains of high field magnetic phase. This results in an intensive light scattering by the crystal. It is shown that the main mechanism of light scattering is related to the large Faraday rotation in the high-field magnetic phase. Visual polarization investigations of the domain structure of the magnetic intermediate state were performed. The energy of domain wall between the antiferromagnetic and the high field magnetic phases was calculated. The region of existence region of the magnetic intermediate state was defined in the H-T coordinates.