Magnetization and magnetic specific heat of terbium

Spin-wave theory, renormalized to take account of spin-wave interactions, is used to calculate the temperature and field dependence of the magnetization of terbium and the temperature dependence of the magnetic contribution to the specific heat. The calculations are based on an interpolation scheme for the spin-wave energies as a function of wave vector and of temperature which gives an approximate fit to the available data obtained by inelastic neutron scattering. Good agreement is found with the magnetization measurements of Hegland, Legvold and Spedding up to about 180 °K. The question of what is the best expression for the internal energy from which to calculate the magnetic contribution to the specific heat is discussed, and calculations are reported based on an expression proposed by Radcliffe. A crude comparison with experimental data of Lounasmaa and Sundström and of Jennings, Stanton and Spedding shows reasonable agreement in view of the approximate nature of the calculations and the method of analysing the data.