Multiferroics refers to compounds where more than one ferroic order such as (anti)ferromagnetism, ferroelectricity, ferroelasticity etc. coexist. The coupling between the various ferroic orders allows for cross-control of the related order parameters, the most important of which is the manipulation of the magnetization or electric polarization by electric or magnetic fields which are relevant in technological applications such as MERAMs or MESO logic. This colloquially makes the term multiferroics synonymous to the coexistence of these ferroic orders. However, the mechanisms leading to the coupling are still debated. One way to describe this coupling is to classify them according to their coupling strength of the orders from independent origins (type I, eg. BiFeO3) to the strong coupling case (type II, eg. TbMnO3) wherein the electric polarization emerges via symmetry-breaking by the magnetic ordering. Recently a new class of multiferroics, the polar magnets (eg. Fe2Mo3O8), is described to have a polar structure in the paramagnetic phase like type I, but the electric polarization emerges only below magnetic ordering like type II, therefore not requiring a particular magnetic structure for the symmetry-breaking and confining both the ferroic order parameters to the same ion. In this presentation, I combined neutron scattering, bulk property measurements and theoretical methods to determine the crystal/magnetic structures, dynamics and electronic structure of several in-house synthesized polar magnets, which are essential for the elucidation of the emergent multiferroicity in these compounds utilizing symmetry concepts. These results will also be compared to other multiferroic “non-polar magnets”.

This work was supported by the University of Missouri Research Council award URC-23-037, "Emergent multiferrocity in novel polar magnets".

Speaker bio: Naren Narayanan studied Materials Science at TU Darmstadt and received his Ph.D. (Dr. rer. nat.) in Condensed Matter Physics and Materials Science at TU Darmstadt and IFW Dresden, Germany in 2010. He was a joint postdoctoral research fellow / postdoctoral researcher at ANSTO, UNSW and ANU, Canberra, Australia before joining MURR as a staff scientist in Aug. 2022. His research interests are broadly in the area of oxides, elucidating the composition-property relationships by investigating their structure and dynamics (excitations). They can be categorized into three parts: Preparation of materials: Synthesis of highly correlated compounds (both single crystals and polycrystalline oxides, especially multiferroics, frustrated spin systems), experimental characterization of them (Neutron and Synchrotron X-ray scattering, bulk properties measurements) and the theoretical modeling and interpretation of the obtained experimental results.