Field-dependence of quantum tunneling in small antiferromagnetic particles

The quantum tunneling of small antiferromagnetic particle is studied in the presence of an external magnetic field at an arbitrary angle. It is found that for antiferromagnetic particle with noncompensated sublattices the Wentzel-Kramers-Brillouin exponent and the crossover temperature from the thermal to the quantum regime depend on the direction and strength of the applied field. This features can be tested with the use of existing experimental techniques. (C) 1999 American Institute of Physics. [S0021-8979(99)04323-4].