Nuclear Magnetic Relaxation Time near Compensation Temperature in Ferrimagnetic Insulator

TL;DR

This study calculates the nuclear magnetic relaxation time in ferrimagnetic insulators, revealing a rapid increase near the compensation temperature due to soft magnon behavior, with implications for ferrimagnet properties.

Contribution

It provides a theoretical analysis of $T_1$ relaxation times near compensation temperatures, highlighting the role of soft magnons and their impact on magnetic relaxation in ferrimagnets.

Findings

1/$T_1$ increases rapidly near $T_0$ on one site.

$T_1$ behavior differs between sites and temperatures.

Soft and hard magnons coexist, affecting magnetic properties.

Abstract

The nuclear magnetic relaxation time $T_1$ in ferrimagnetic insulators is calculated by a Raman process of hyperfine interaction with a meanfield approximation. It is found that the 1/$T_1$ on one site rapidly increases near the compensation temperature $T_0$, whereas that on another site does not increase up to Curie temperature $T_c$. This is due to that the band width of soft magnon becomes comparable to $T_0$. The increasing behavior of 1/$T_1$ below $T_c$ 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/$T_1$ below $T_c$, even though the magnetization does not show the compensation. Such a coexistence of soft and hard magnons will lead to remarkable properties of ferrimagnet.