RESONANT SPIN TUNNELING IN SMALL MAGNETIC PARTICLES

A new macroscopic test of spill tunneling in single-domain magnetic pa rticles is proposed. It is shown that quantization of spin, even in pa rticles of a considerable size, may lead to a detectable zero-field ma ximum in the dependence of the rate of the magnetic relaxation on the magnetic field. This effect must be especially pronounced in antiferro magnetic particles. It is argued that recent observation by several gr oups of the non-monotonic field dependence of the blocking temperature in ferritin may, in fact, present the experimental evidence of this e ffect. (C) 1998 Elsevier Science B.V. All rights reserved.