The modulated antiferromagnetic structures in multiferroic FeVO4: a 57Fe M\"ossbauer spectroscopy investigation

TL;DR

This study uses 57Fe Mössbauer spectroscopy to analyze the magnetic structures of FeVO4, confirming and quantifying the incommensurate elliptical and collinear modulated phases in agreement with neutron diffraction data.

Contribution

It introduces specific lineshapes for Mössbauer spectra to accurately characterize elliptical and collinear magnetic structures in multiferroic FeVO4.

Findings

Elliptical hyperfine field modulation persists at T=0.

Spectroscopic results agree with neutron diffraction data.

Hyperfine interaction anisotropy explains the T=0 modulation.

Abstract

We present a 57Fe M\"ossbauer spectroscopy study of the two incommensurate magnetic phases in the multiferroic material FeVO4. We devise lineshapes appropriate for planar elliptical and collinear modulated magnetic structures and show that they reproduce very well the M\"ossbauer spectra in FeVO4, in full qualitative agreement with a previous neutron diffraction study. Quantitatively, our spectra provide precise determinations of the characteristics of the elliptical and modulated structures which are in good agreement with the neutron diffraction results. We find that the hyperfine field elliptical modulation persists as T goes to 0, which we attribute to an anisotropy of the hyperfine interaction since a moment modulation is forbidden at T=0 for a spin only ion like Fe3+.