Rotational States of Magnetic Molecules

TL;DR

This paper investigates the quantum states of a magnetic molecule capable of spin tunneling and rotation, revealing how the interplay of spin, inertia, and tunneling influences its magnetic properties.

Contribution

It provides an exact solution for low-energy eigenstates of a rotating magnetic molecule with spin tunneling, highlighting the role of a key parameter in its ground state behavior.

Findings

Ground state magnetic moment depends on parameter α.

Magnetic moment is zero below critical α, non-zero above.

Spin localizes along the anisotropy axis as α approaches infinity.

Abstract

We study a magnetic molecule that exhibits spin tunneling and is free to rotate about its anisotropy axis. Exact low-energy eigenstates of the molecule that are superpositions of spin and rotational states are obtained. We show that parameter $\alpha = 2(\hbar S)^2/(I\Delta)$ determines the ground state of the molecule. Here $\hbar S$ is the spin, $I$ is the moment of inertia, and $\Delta$ is the tunnel splitting. The magnetic moment of the molecule is zero at $\alpha < \alpha_c = [1-1/(2S)^{2}]^{-1}$ and non-zero at $\alpha > \alpha_c$. At $\alpha \to \infty$ the spin of the molecule localizes in one of the directions along the anisotropy axis.