Spin dynamics in molecular ring nanomagnets: Significant effect of acoustic phonons and magnetic anisotropies

TL;DR

This study investigates how acoustic phonons and magnetic anisotropies significantly influence spin dynamics and relaxation rates in molecular ring nanomagnets, aligning theoretical models with experimental data.

Contribution

It provides a comprehensive calculation of nuclear spin-lattice relaxation rates considering both magnetic anisotropies and acoustic phonons, enhancing understanding of spin dynamics in ring nanomagnets.

Findings

Relaxation rate 1/T_1_ peaks near k_B_T=|J| for various J values.

Magnetic anisotropies and acoustic phonons are crucial for matching experimental results.

The model reproduces experimental data for Cu^II^ ring clusters.

Abstract

The nuclear spin-lattice relaxation rate 1/T_1_ is calculated for magnetic ring clusters by fully diagonalizing their microscopic spin Hamiltonians. Whether the nearest-neighbor exchange interaction J is ferromagnetic or antiferromagnetic, 1/T_1_ versus temperature T in ring nanomagnets may be peaked at around k_B_T=|J| provided the lifetime broadening of discrete energy levels is in proportion to T^3^. Experimental findings for ferromagnetic and antiferromagnetic Cu^II^ rings are reproduced with crucial contributions of magnetic anisotropies as well as acoustic phonons.