Temperature Increase of Highly-Polarized Fermi Liquids in Spin-Echo Experiments

We show that there are restrictions on the maximum tipping angle that can be used without significantly raising the temperature of the 3 He distribution in high B/T spin-echo experiments with pure liquid 3 He and 3 He- 4 He solutions. The temperature increase occurs during the diffusion process as quasiparticles in mixed-spin states are scattered and converted into thermal excitations at the spin-up and spin-down Fermi surfaces. This temperature increase can mimic the effects of zero temperature attenuation, leading to a higher values of the measured anisotropy temperature Ta. We analyze the dependence of the increase on polarization, initial temperature, 3 He concentration, and tip angle, and estimate the size of the effect in recent experiments.