Magnetization of rare earth metals along axis of hard magnetization

A system of equation has been formulated in the molecular field approximation for calculating magnetization of anisotropic ferromagnets when an external magnetic field is oriented in the direction of hard magnetization. The numerical solution of equations for Tb,Dy,Ho,Er,Tm is performed by a computer and is compared with experimental results. It is shown, that when H=Hsub(a) (Hsub(a) is the effective field of anisotropy), susceptibility diverges logarithmically, that is considered as a second-order phase transition, magnetization being continuous. The numerical experiment carried out by the authors does not contradict this result. Temperature dependence of the deflection angle of the magnetic moment from the magnetic field direction is obtained. Some deflection of M from H with T increasing obtained in the range of low temperatures for Tb and Ho is related to different temperature dependences of the anisotropy constant of various orders. The experimental results for Ho, Er and Tm agree well with the calculations. A formula for calculating the Curie paramagnetic temperature for an arbitrary direction is given