Geometric-Phase-Effect Tunnel-Splitting Oscillations in Single-Molecule Magnets with Fourth-Order Anisotropy Induced by Orthorhombic Distortion

TL;DR

This paper investigates how orthorhombic distortion-induced fourth-order anisotropy affects tunnel-splitting oscillations in single-molecule magnets, revealing interference effects that modulate tunneling without external magnetic fields.

Contribution

It introduces an instanton-based analysis of interference effects caused by combined second- and fourth-order anisotropies in spin tunneling.

Findings

Tunnel splitting exhibits periodic zeros as second-order anisotropy increases.

Interference of four tunneling paths causes oscillations in tunnel splitting.

Effect occurs without external magnetic field.

Abstract

We analyze the interference between tunneling paths that occurs for a spin system with both fourth-order and second-order transverse anisotropy. Using an instanton approach, we find that as the strength of the second-order transverse anisotropy is increased, the tunnel splitting is modulated, with zeros occurring periodically. This effect results from the interference of four tunneling paths connecting easy-axis spin orientations and occurs in the absence of any magnetic field.