NMR studies on vortices in rotating3He-A

NMR measurements are reported on rotating³He-A in a long cylindrical geometry of 5 mm diameter at a liquid pressure of 29.3 bar and in axial magnetic fields of 14.2, 28.4, and 56.9 mT. At 28.4 mT, NMR studies are also reported in fields inclined by 25° and 90° from the axis of rotation. The frequency shift, the width, and the intensity of the spin wave modes localized on the soft vortex cores, as well as the additional broadening of the main NMR line during rotation, were measured as a function of temperature, angular velocity , magnetic field intensity, and its inclination angle. Also observed were a critical angular velocity of vortex formation, hysteretic behavior in the number of vortices when comparing accelerating rotation to decelerating, and metastable vortex densities, presumably a vortex tangle after rapid oscillatory acceleration. The results can be understood in terms of the continuous 4 vortices first proposed by Seppälä and Volovik.