Resonant spin tunneling in small magnetic particles

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