Nuclear spin-lattice relaxation in ferrimagnetic clusters and chains: A contrast between zero and one dimensions

Abstract

Motivated by ferrimagnetic oligonuclear and chain compounds synthesized by Caneschi et al., both of which consist of alternating manganese(II) ions and nitronyl-nitroxide radicals, we calculate the nuclear spin-lattice relaxation rate ${1/T}_{1},$ employing a recently developed modified spin-wave theory. ${1/T}_{1}$ as a function of temperature drastically varies with the location of probe nuclei in both clusters and chains, though the relaxation time scale is much larger in zero dimension than in one dimension. ${1/T}_{1}$ as a function of an applied field in long chains forms a striking contrast to that in finite clusters, diverging with decreasing fieldlike inverse square root at low temperatures and logarithmically at high temperatures.