The modulated antiferromagnetic structures in multiferroic FeVO4: A 57Fe Mössbauer spectroscopy investigation

Abstract : We present an investigation of the two incommensurate magnetic phases in the multiferroic material FeVO4 using magnetic susceptibility and 57Fe Mössbauer spectroscopy measurements. The susceptibility shows anomalies at the phase transitions at 15.7 and 23 K. We devise Mössbauer lineshapes appropriate for planar elliptical and collinear modulated magnetic structures and show that they reproduce very well the Mössbauer 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 match rather well the neutron diffraction results. We find that the hyperfine field elliptical modulation persists as T→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+.