Quantum interference in small magnetic particles

We consider tunneling of a large spin between nonequivalent wells in the presence of the magnetic field. Using coherent spin states we show that the quenching of tunneling for a half-integer spin, which occurs at H=0, survives up to a reasonably large field. An experiment is proposed which may allow one to observe this quenching. Oscillation of the tunneling rate on the applied field is suggested. © 1993 The American Physical Society.