Evidence for multimagnon-mediated nuclear spin relaxation in the intertwining double-cain ferrimagnet $Ca_3 Cu_3 (PO_4)_4$

TL;DR

This study measures the nuclear spin-lattice relaxation time in a ferrimagnet and reveals that three-magnon processes, rather than Raman processes, dominate spin dynamics, introducing a new understanding of one-dimensional ferrimagnetic behavior.

Contribution

First measurement of $^{31}P$ nuclear spin relaxation time in $Ca_3 Cu_3 (PO_4)_4$ and identification of three-magnon processes as the main relaxation mechanism.

Findings

$T_1$ measured for the first time in this compound.

Three-magnon processes are the dominant relaxation mechanism.

Modified spin-wave theory explains the relaxation behavior.

Abstract

The nuclear spin-lattice relaxation time $T_1$ of $^{31}P$ nuclei in the title compound is measured for the first time and interpreted in terms of a modified spin-wave theory. We establish a novel scenario for one-dimensional ferrimagnetic spin dynamics -- it is three-magnon processes enhanced by exchange scattering, rather than Raman processes, that make the major contribution to $1/T_1$.