  We perform constant pressure Monte Carlo simulations of a spin-analogous
model which describes coupled spatial and magnetic degrees of freedom on an fcc
lattice. Our calculations qualitatively reproduce magnetovolume effects
observed in some rare earth manganese compounds, especially in the anti-Invar
material YMn2. These are a sudden collapse of the magnetic moment which is
connected with a huge volume change, and a largely enhanced thermal expansion
coefficient.
