Evidence for Multimagnon-Mediated Nuclear Spin Relaxation in the Intertwining Double-Chain Ferrimagnet Ca3Cu3(PO4)4

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 $1/T_1$.
Comment: 6 pages with 7 figures embedded