Magnetization of a uniaxial ferromagnet with single-ion and exchange anisotropies in a transverse magnetic field

Two-time temperature Green functions are used for calculating the magnetization of uniaxial ferromagnet with single-ions anisotropy and exchange anisotropy in transversal magnetic field. In the random phase approximation the expressions for magnetization and anisotropy field (HA) are obtained for arbitrary temperature, spin and anisotropy energy parameters. The results obtained are valid for one- and two-sublattice anisotropic ferromagnets. For magnetic field $H=H_A$ the low-temperature magnetization dependence is shown to reduce in certain cases to the power law with the degree one.