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

TL;DR

This paper investigates nuclear spin-lattice relaxation in ferrimagnetic clusters and chains, revealing how relaxation rates vary with temperature, magnetic field, and dimensionality, using a modified spin-wave theory.

Contribution

It introduces a detailed comparison of relaxation behaviors in zero- and one-dimensional ferrimagnetic systems using a novel theoretical approach.

Findings

Relaxation rate 1/T_1 varies significantly with probe location.

Zero-dimensional clusters have much longer relaxation times than chains.

In chains, 1/T_1 diverges as the magnetic field decreases, with distinct temperature dependencies.

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 field like inverse square root at low temperatures and logarithmically at high temperatures.