dr. Eric Langenberg: Ferroic Transition Metal Oxides: Engineering novel Functionalities

Abstract

First part of the talk is devoted to Bi-compounds, namely BiMnO3 and doubleperovskite (Bi,La)2NiMnO6. Despite being promising multiferroic candidates, we can only demonstrate that (Bi,La)2NiMnO6 shows clear ferroelectric features, questioning the ferroelectric character of BiMnO3. Moreover, in disagreement with previously reported magnetoelectric data, the coupling between the ferroelectric and magnetic order points to be weak in these compounds, especially in (Bi,La)2NiMnO6, which is likely related to the different mechanisms generating ferroelectricity (off-centring lonepair electrons Bi3+) and magnetism (superexchange interaction between transition metal cations through adjacent oxygen anions). In order to overcome the scarcity of multiferroics showing strong magnetoelectric coupling, the second part of the talk is focused on the alkaline-earth manganite system, in particular (Sr1-xBax)MnO3 (SBMO) thin films. Here Mn4+ is expected to drive both the magnetic order and the required non-centrosymmetric distortion for ferroelectric order.