Orientation of the angular momentum in superfluid ³He-A in a stretched aerogel

Superfluid ³He-A in a fully characterized stretched aerogel, used in previous work by Pollanen et al., has been studied for parallel and perpendicular orientations of the magnetic field relative to the anisotropy axis of the aerogel. Consistently, we find that an equal spin pairing state (ESP) is stabilized down to the lowest temperature. From our pulsed NMR frequency shifts as a function of temperature and tip angle, the orientation of the orbital angular momentum l̂ has been determined. The aerogel anisotropy introduced by uniaxial stretching tends to align l̂ in the axial state parallel to the strain axis, consistent with the theory proposed by Sauls and contrary to Volovik's prediction based on an impurity calculation of Rainer and Vuorio.