Direction ofA1pairs in superfluidHe3: Paramagnon model revisited

In a previous paper it was argued that an important test of the paramagnon-induced pairing mechanism in superfluid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ would be to determine the direction of pairs in the $A_1$ phase. A calculation within the paramagon model which did not include effective-mass corrections implied that the spin alignment should be opposite to that deduced from the usual "weak-coupling" mechanism, in which the attractive pairing interaction is independent of the magnetic field $H$. Here we show that a proper inclusion of the mass enhancement factor within the paramagnon model implies that the pairs in the $A_1$ phase align in the same direction as that predicted by a weak-coupling mechanism. The magnitude of this effect is in very good agreement with experiment. Recent experiments published after this work was completed now suggest that the measured sign is also in accord with the prediction presented here.