Anomalous Volume Expansion and Magnetovolume Effect in Cu–Mn

The relation of anomalous volume expansion of Cu–Mn with concentration is elucidated on the basis of the virial theorem and the electronic structure which is calculated with use of the CPA. The origin of the volume expansion is the loss of the bonding energy due to the growth of the magnitude of the Mn local magnetic moment with decreasing Mn concentration. In connection with this problem, it is found that the magnetic pressure is approximately equal to a linear combination of squares of local magnetic moments, which gives a justification for the empirical formula in the magnetovolume effect. The bulk modulus of Cu–Mn and the P - Y relation of γ Mn are also calculated.