Multiferroic rust: magnetoelectric effect in g\"{o}thite, $\alpha$-FeOOH

TL;DR

This study demonstrates that goethite, a common mineral, exhibits a linear magnetoelectric effect below 400 K, with potential for widespread natural applications due to its abundance.

Contribution

The paper reveals that goethite is a natural, widespread magnetoelectric material with a measurable magnetoelectric coefficient, supported by symmetry analysis, DFT calculations, and Monte Carlo simulations.

Findings

Goethite exhibits a linear magnetoelectric effect below 400 K.

Magnetic field induces a spin-flop phase transition affecting electric polarization.

Calculated magnetoelectric coefficient is 0.24 μC/m²·T.

Abstract

By means of symmetry analysis, density functional theory calculations, and Monte Carlo simulations we show that goethite, $\alpha$-FeOOH, is a linear magnetoelectric below its N\'{e}el temperature $T_{\rm N}=400$ K. The experimentally observed magnetic field induced spin-flop phase transition results in either change of direction of electric polarization or its suppression. Calculated value of magnetoelectric coefficient is 0.24 $\mu$C m$^{-2}$ T$^{-1}$. The abundance of goethite in nature makes it arguably the most widespread magnetoelectric material.