Spin relaxation phenomena in the 3He-A1 phase. Effects of magnetic field profile,spin counterflow,and 4He coverage

We report observations on the effects of the magnetic field profile and surface coverage by ⁴He on the magnetically driven superflows in the ³He-A₁ phase. When the gradient magnetic field profile is changed: (1) an unexpected reversal in the direction of superflow is observed, and (2) the relaxation time of the induced pressure increases in the warmer region of the A₁, phase but remains constant in the colder region. When the surfaces in the apparatus are covered with ⁴He: (1) the induced pressure amplitude decreases and the relaxation time increases and saturates at about twice that of pure ³He in the warmer side of the phase, and (2) the relaxation time is independent of the ⁴He coverage in the colder side. We give qualitative interpretation of the observed effects in terms of spin density relaxations; in the warmer side of the phase the spin density relaxes via processes in both bulk liquid and surface boundary and in the colder side the spin relaxation is dominated by connective spin counterflows in the A₂/A phase liquid in the fringing field of the static magnetic field.