Bar'yakhtar–Krivoruchko–Yablonskii representation and thermodynamics of magnetically ordered systems

The thermodynamics of a Heisenberg ferromagnet is studied on the basis of the Bar'yakhtar–Krivoruchko–Yablonskii method. The interaction of the elementary excitations is taken into account in the generalized selfconsistent field approximation. The approach leads to results that at low temperatures are identical to Dyson's results and make it possible to obtain an interpolation description of the thermodynamic functions in the complete region of temperatures in which an ordered phase exists.