BEHAVIOUR OF SPECIFIC HEAT Cp THERMAL EXPANSION β & COMPRESSIBILITY KT NEAR MAGNETIC TRANSITIONS

Abstract

The Ehrenfest relations for second order phase transitions are shown to be  unsuitable near ferromagnetic/antiferromagnetic-to-paramagnetic transitions, which  show logarithmic or other infinities in specific heats. The applicability of the more  general Pippard relations in such cases is investigated.  Cp  and  B of  Gd, Ni (ferromagnets) and MnF2, MnO. MnTe (antiferromagnets) below the transition Tc, are  correlated well with the change of Tc with pressure. For chromium, Kr  and B  below  Tc  are also related to the pressure derivative of Tc. The effect of specimen purity  is noticed in few cases. The Pippard scheme is free from the deficiencies of the  Ehrenfest relations when correlating  Cp,  B and kr near L-transitions.