Magnetic properties of the TbMn6Sn6 compound

Magnetic properties of the TbMn6Sn6 compound in the temperature range 4.2-310 K were investigated. The magnetization jumps observed upon magnetization along the hard magnetization direction are shown to be due to the first-order magnetic-field-induced spin-reorientation transitions (SRT). The magnetization curves were described within a phenomenological model of magnetization with allowance for two constants of magnetocrystalline anisotropy K-1 and K-2. Their numerical values were obtained. Neutron diffraction study of the TbMn6Sn6 compound in an external magnetic field was carried out. The values and orientations of magnetic moments of the Tb and Mn sublattices before and after SRT were determined. The values of the K-1 constant and of the constant of intersublattice exchange interaction n(TbMn) (6.3 to 10.1 x 10(6) J/m(3) and 4.2 to 6.2 T f.u/mu(B), respectively) were obtained from a numerical analysis of the magnetization curve measured along the hard magnetization direction in an oriented TbMn6Sn6 sample at 4.2 K. The magnetic-field dependences of the linear and volume magnetostrictions of an isotropic TbMn6Sn6 sample correlate well with jumpwise magnetization processes. The major hysteresis loops were measured and the values of the coercive force were determined in a wide temperature range.