MONTE-CARLO SIMULATIONS OF HIGH-MOMENT LOW-MOMENT TRANSITIONS IN INVAR-ALLOYS

We have reproduced magneto-volume effects typical for Invar alloys by examining a. spin-analogous model which describes coupled spatial and magnetic degrees of freedom and, additionally, chemical disorder. Cons tant pressure Monte Carlo simulations of this model show an almost van ishing thermal expansion over a broad range of temperatures below T-C, a softening of the bulk modulus and the absence of a sharp peak in th e specific heat at the magnetic phase transition as observed in Fe65Ni 35 Invar.