Probing of order parameters in magnetoelectric multiferroics by neutron diffraction

Abstract

Neutron scattering methods are indispensable in studying structure-property relationships. Determination of spin arrangements in magnetically ordered materials makes neutron diffraction among the major tools in the research on multiferroics because to understand why a given compound displays or does not display the expected properties calls for detailed information on microscopic level. We describe the efforts to identify new candidate magnetoelectric materials based primarily on considerations of symmetry and the knowledge of the magnetic structure. We found that substitution of half manganese with iron introduces a low level of disorder between the two transition metal positions in the RFeMnO5 (R=Tb,Yb) structure. The lack of evidence for a crystallographic phase transition to a polar space group rules out expectations of a spontaneous electric polarization. In addition, the observed collinear magnetic structure with k = 0 does not permit a spin polarization.. Therefore, by contrast to well known multiferroics RMn2O5 (R=Tb,Yb), YbMnFeO5 and TbMnFeO5 is not expected to be multiferroic compounds. Other examples in this article include nanosize powder material from the mixed oxide system YFexCr1−xO3 and Y-type hexaferrite multiferroic Ba2Mg2Fe12O22 as well as antiferromagnetic La0.5Pb0.5FeO3.