Nuclear Magnetic Relaxation Time near Compensation Temperature in Ferrimagnetic Insulator
Abstract
The nuclear magnetic relaxation time T1 in ferrimagnetic insulators is calculated by a Raman process of hyperfine interaction with a meanfield approximation. It is found that the 1/T1 on one site rapidly increases near the compensation temperature T0, whereas that on another site does not increase up to Curie temperature Tc. This is due to that the band width of soft magnon becomes comparable to T0. The increasing behavior of 1/T1 below Tc is found also in another type ferrimagnet, which shows hump structure in the temperature dependence of magnetization instead of compensation. Also in this case, we find the rapid increase of 1/T1 below Tc, even though the magnetization does not show the compensation. Such a coexistence of soft and hard magnons will lead to remarkable properties of ferrimagnet.