Magneto-optical investigation of magnetic field induced spin-reorientational phase transition in Hosub(0,8)Ysub(2,2)Fesub(5)Osub(12) at 4.2 K

Phase transition of the first order not manifesting in change of magnetization is disclosed when investigating into the dependence of the rotation angle of the main axis in the ellipse of light polarization in ferrite-garnet Hosub(0.8)Ysub(2.2)Fesub(5)Osub(12) at 4.2 K on the external magnetic field applied along <111> at H approximately 25 kOe. This transition is interpreted to be spin-reorientati.onal. It is shown that tWo-beam-refraction is rather sensitive to the observed transition. Numerical calculation has revealed that the solution obtained in a supposition on the Ising nature of magnetic moments of Ho3+ ions is stable to the magnitude of their real anisotropy. For explanation of magnetic and magnetooptical properties of Hosub(x)Ysub(3-x)Fesub(5)Osub(12) near the compensation point by composition it is necessary to take into account the iron sublattice anisotropy as well as uniaxial anisotropy induced during the crystal growth