Investigation of the crystal and magnetic structures of the trigonal multiferroic iron-boracite Fe3B7O13(OH)

TL;DR

This study uses neutron diffraction to elucidate the crystal and magnetic structures of Fe3B7O13(OH), revealing its magnetic ground state, absence of monoclinic distortion, and notable magnetic frustration despite a stable magnetic moment.

Contribution

It provides the first detailed neutron diffraction analysis of Fe3B7O13(OH), clarifying its magnetic structure and properties within the boracite family, including the role of hydroxyl groups.

Findings

No monoclinic distortion in magnetic state

Fe3B7O13(OH) has the highest magnetic frustration in the series

Magnetic moment remains stable despite high frustration

Abstract

We have investigated the crystal and magnetic structures of the trigonal iron-boracite Fe3B7O13X with X = OH by neutron diffraction. Neutron diffraction enables us to locate the hydrogen atom of the hydroxyl group and determine the magnetic ground state of this member of the multiferroic boracite family. No evidence was found for a monoclinic distortion in the magnetic ordered state. The magnetic symmetry allows for magnetoelectric and ferroelectric properties. The N/'eel tempera- ture TN of 4.86(4) K confirms the general trends within the boracites that TN decreases from X = I > Br > Cl > OH. Surprisingly while Fe3B7O13OH exhibits the largest frustration with $|\theta/T_N| = 5.6$ within the Fe3B7O13X series, no reduction of the magnetic moment is found using neutron diffraction.