Surface spin waves in 3He-A, a probe for vortex phenomena in narrow gaps

We report measurements on a new collective spin-wave mode trapped by the textural boundary layers of 3He-A within a stack of thin Mylar plates. The surface mode was seen as a new peak in the cw NMR spectrum measured at H0=284 Oe. Rotation of the sample, with orthogonal to the gaps, increased the spectral weight of the surface mode, indicating an increase in the textural boundary layers caused by a counterflow-induced transition. This phenomenon was used to study vortex creation and persistent currents.