Relationship between the heat capacity, thermal expansion coefficient, and spontaneous magnetization in the invarlike compound YFe10Mo2

Heat capacity, thermal expansion coefficient (TEC), and spontaneous magnetization of the ferromagnetic compound YFe10Mo2 with a Curie temperature T C = 390 K have been investigated in the temperature range from 2 to 400 K. Relationships between the temperature dependences of the magnetic part of heat capacity (C m), the magnetic part of the thermal expansion coefficient (αm), and the spontaneous magnetization (M s) for the compound YFe10Mo2 have been considered. It has been found that the magnetic part of the heat capacity can be approximated well by a dependence C m(T) = a × dM s 2 /dT − b × dM s 4 /dT with a > 0 and b s> 0, and the magnetic part of the TEC, by a dependence αm = A × dM s 2 /dT + B × dM s 4 /dT with A > 0 and B > 0 in the entire range of temperatures of magnetic ordering. It is assumed that the basic sources in the formation of the observed C m(T) and αm(T) dependences are the changes in the elastic, magnetoelastic, magnetovolume, and magnetostatic energies of the sample, which appear as a result of the spontaneous magnetostrictive deformation with a change in temperature. A comparison of the results obtained for YFe10Mo2 with the results of the approximation of the C m(T) and αm(T) dependences on dM s 2 /dT and dM s 4 /dT and on the basis of data available for the Invar alloy Fe65Ni35.