Stabilization of homogeneously precessing domains by large magnetic fieldsin superfluid He-3-B

We have studied the catastrophic relaxation in superfluid (3)Hr-B as a func tion of magnetic field for a sample pressure of 31 bars. "Catastrophic rela xation" refers to a novel magnetic relaxation process which rapidly disrupt s the homogeneous precession of nuclear spins in NMR experiments on the B p hase. The catastrophe was observed through its effect on the evolution of a long-lived coherent dynamic state, the homogeneously precrssing domain. Ou r measurements reveal that the onset of catastrophic relaxation is suppress ed to lower temperatures by a strong magnetic field.