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 3He distribution in high B/T spin-echo experiments with pure liquid 3He and 3He-4He 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, 3He concentration, and tip angle, and estimate the size of the effect in recent experiments.