Temperature Dependence of the Spontaneous Magnetization in Holmium Nitride

On the assumption that each Ho +3 ion has the two lowest lying levels, the temperature dependence of the spontaneous magnetization of HoN is discussed by a spin wave approximation. The approximate spin wave functions considered in the present study are so constructed as to include the basal wave functions for the one ion Hamiltonian composed of the terms of the cubic crystalline fields and the effective exchange field parallel to <100>. This numerical computations are carried out by using the numerical data of previous papers. Due to the partial quenching of the angular momentum, the averaged z-component of the total angular momentum J over these wave functions is found to be reduced essentially from J=8 in free state. The temperature dependence of the spontaneous magnetization of HoN departs from the usual Bloch T 3/2 law and is well in accordance with the experimental data.