Renormalized Spin Wave Theory of Nearly Two-Dimensional Ferromagnet K₂CuF₄

Abstract

The temperature and the magnetic field dependences of the magnetization of the ferromagnetic layer-type compound K 2 CuF 4 have been analyzed by the spin wave theory which takes into account the spin wave interaction. It is shown that the spin wave interaction plays rather important role in the nearly two-dimensional magnetic system and gives rise to a logarithmic term in the expansion of the magnetization with respect to the temperature. The apparent T 3/2 temperature dependence of the magnetization can be shown to be realized in a certain temperature region. With the use of the exchange interaction constants estimated in the previous investigations, the present calculation shows excellent agreements with the experiments.