The part played by magnetoelastic interaction in the forming of thermodynamic functions of ferromagnets: Second thermodynamic derivatives of thermodynamic potential

This is a continuation of the previously [1] started consistent construction of thermodynamics of ferromagnets, the magnetic ordering of which may be considered in the spirit of Landau's phenomenological approach but in view of magnetoelastic interaction (MEI) between magnetic subsystem and crystal lattice. Thermodynamically exact expressions are obtained within the model for second thermodynamic derivatives of the thermodynamic potential renormalized in view of MEI. Model calculations are performed on the real scale of temperatures in the absence of magnetic field, the results of which demonstrate that the developed approach in view of MEI produces much better qualitative and quantitative agreement with the actually observed behavior of the thermodynamic functions of ferromagnets than the traditional Landau theory.