Nuclear magnetic relaxation time near the compensation temperature in a ferrimagnetic insulator

フェリ磁性絶縁体の補償温度近傍における核磁気緩和時間

森 道康  

Mori, Michiyasu

The nuclear magnetic relaxation time in a ferrimagnetic insulators is calculated within the mean-field approximation for the magnetic exchange interactions and the Raman process involving the hyperfine interaction. We find that the value of 1/ on one type of site increases rapidly near the compensation temperature , whereas that on the other type of site does not increase up to Curie temperature . This is due to the fact that the soft-magnon bandwidth becomes comparable to . An increase in 1/ below is found also in another type ferrimagnet, which shows a hump structure in the temperature dependence of magnetization instead of compensation. Also in that case, we find the rapid increase in 1/ below , even though the magnetization does not show compensation. The coexistence of soft and hard magnons leads to these remarkable properties of ferrimagnets.