VIBRATIONAL AND MAGNETIC CONTRIBUTION TO ENTROPY OF AN L1(2) ORDERED AND A PARTIALLY ORDERED NI3MN ALLOY - RESULTS FROM THERMAL-EXPANSION MEASUREMENTS AND MODEL-CALCULATIONS

Thermal expansion measurements have been performed on an Lit ordered a nd a quenched Ni3Mn alloy and the role of electrons, phonons and magne tic moments on their thermodynamic properties has been studied using t heoretical models. We show that with increasing atomic disorder the it inerant nature of the electron moments decreases. We furthermore show that magnetic interactions do not influence the chemical ordering of N i3Mn, while lattice vibrations play an important role in its ordering transition.