Anomalous Attenuation of Spin-Entropy Waves in SuperfluidHe−3A1

The propagation of spin-entropy waves was observed in superfluid ${}_{}{}^3{}_{}{}^{}\mathrm{H}\mathrm{e}-A_1$ at a pressure of 22.7 bars and magnetic fields up to 5 T. A large increase in attenuation was observed within the $A_1$ phase near its lower transition temperature to the $A_1$ phase over an unexpectedly large temperature width. The observed effects are suggested as evidence for the presence of a minority (down-moment pair) condensate population predicted by Monien and Tewordt.