SURFACE EFFECTS ON THE MAGNETIC-BEHAVIOR OF ANTIFERROMAGNETIC PARTICLES

Antiferromagnetic particles can exhibit the phenomenon of superparamag netism if the number of spins in the two sublattices is unequal (''unc ompensated spins''). Monte Carlo simulations have been performed on sp herical particles in which the spins interact with classical Heisenber g interactions. Anisotropy effects are also included with distinct for ms in the core and at the surface. The magnetization was calculated as a function of both temperature and applied magnetic field for a range of particle sizes. Different types of behavior are found which depend on the number of uncompensated spins. Certain field dependent behavio r is shown to scale with the ratio of the number of uncompensated to t he total number of spins. (C) 1998 American Institute of Physics. [S00 21-8979(98)03017-5]