Linear Magnetoelectric Effect by Orbital Magnetism

TL;DR

This paper demonstrates that the linear magnetoelectric effect can arise from the response of orbital magnetic moments to electric-field-induced polar distortions, using symmetry analysis and first principles calculations on LiFePO4.

Contribution

It reveals a new mechanism for the linear magnetoelectric effect based on orbital magnetism and spin-orbit coupling, expanding understanding of magnetoelectric phenomena.

Findings

Orbital magnetic moments are partially unquenched by spin-orbit coupling.

Electric fields can modify orbital magnetic moments, inducing linear magnetization.

The mechanism is demonstrated in LiFePO4 through first principles calculations.

Abstract

We use symmetry analysis and first principles calculations to show that the linear magnetoelectric effect can originate from the response of orbital magnetic moments to the polar distortions induced by an applied electric field. Using LiFePO4 as a model compound we show that spin-orbit coupling partially lifts the quenching of the 3d orbitals and causes small orbital magnetic moments ($\mu_{(L)}\approx 0.3 \mu_B$) parallel to the spins of the Fe$^{2+}$ ions. An applied electric field $\mathbf{E}$ modifies the size of these orbital magnetic moments inducing a net magnetization linear in $\mathbf{E}$.