Critical properties of Heisenberg ferromagnets with lattice inhomogeneity

Two types of lattice inhomogeneity were studied by self-consistent Monte Carlo calculations. The critical isotherm of a system with a free surface can be described by a power law m 1 approximately h 1 delta 1/ for the surface-layer magnetization with a critical exponent delta 1 =2.3+or-0.1, fulfilling the recently proposed scaling relations satisfactorily. A homogeneous system with a missing cluster of 2 3 spins was investigated in zero field. The critical behaviour of the local order parameter m 1 approximately (-t) beta 1 close to this defect shows a changeover for beta 1 :0.33