Suppression of π/2−π Spin Echo in Solid 3He in High Fields

Abstract

High demagnetizing field in solid 3He leads to rich interesting phenomena such as multiple spin echoes. On the other hand, it has a severe influence on the appearance of the ordinary spin echo using π/2−π RF pulse sequence. We have observed spin echoes in solid 3He in 7.4 Tesla, which appeared to decay on a much shorter time scale than T2 estimated from theories. This can be explained as follows. The angle made by the magnetization with the field after the π-pulse differs a little from that before the pulse, because the π-pulse employed in the experiment is inevitably not ideal. Since due to the demagnetizing field, the frequency of the precession motion depends on the angle between the magnetization and the field, the frequencies before and after the π-pulse are different, which smeared out the spin echo. We have computed the damping time in various conditions, and found good agreement with experimental results.