RESONANT OBSERVATION OF THE LANDAU FIELD IN SUPERFLUID HE-4-B BY NMR

We report the first experimental observation of the internal precession of the normal and superfluid magnetizations around the molecular Landau field in He-3-B. This mode is excited by cross relaxation with the conventional NMR precession of the total magnetization around an external field when the two fields have similar values. From NMR measurements down to 0.12T(c) we conclude that the catastrophic relaxation phenomenon can be explained as a capture of the internal-precession mode by the Larmor precession. Values of the crossover temperature are estimated for a number of pressures.