The total heat capacity of the Nd2Hf2O7 material contains two parts C(T)=Clat(T)+Cmag(T) where the first term is associated to the lattice vibrations while the second is associated to the spin contribution.

The first term ins independent on the magnetic field and dominates at high temperature, whereas the second input depends on both the temperature and the magnetic field, and becomes significant at temperatures of ~ S.J/kB. The lattice contribution may be evaluated using the Debye model

Clat(T)=9 n NAkB(T/TD)3 * integral[ over 0, T/TD]{y4 exp(y)dy/(exp(y)-1)2)}

where where n is the number of atoms per formula unit, NA is

Avogadro’s number, and TD is the Debye temperature.

You will need to know TD and n for your material.

However t, if you subtract the heat capacity of the non-magnetic pyrochlore Lu2Hf2O7 from the above heat capacity data C(T), you can obtain a rough value the magnetic contribution of Nd2Hf2O7: Cmag(T)= C(T)-Clat(T)

Thank you for your reply Dr. Mohamed El Hafidi. I was actually looking for the formula for mass and volume corrections as Nd2Hf2O7 and Lu2Hf2O7 have different formula masses and different unit cell volumes. For getting correct value of magnetic contribution, i need to correct heat capacity data of Lu2Hf2O7 by applying mass and volume corrections and then perform the subtraction. Anyway, thanks for your response.