The project steps outside the boundaries of the transition metal oxide compounds, mostly studied up to now, to investigate oxyborates with the ludwigite structure M3+(M2+)2O2BO3 (M is a transition element, divalent or trivalent). It associates mixed valence (di- and tri-valent ions) with a low dimensional network of transition metal atoms. The aim of the project is to characterize in details compounds belonging to this system, to identify new multiferroics/magnetoelectrics. Giant magnetoelectric effects have already been observed in Fe3BO5, but vast possibilities remain to induce such an effect by playing with substitution on the 2+ or 3+ sites of another transition element or a rare-earth element, or by random site disorder by a non-magnetic element. On the technical side, the project will rely on the thorough characterizations of chosen oxyborate compositions, combining local and larger scale structural and physical characterization techniques (X-ray and neutron diffraction [LLB]), with physical properties measurements (transport, magnetization, dielectric constant, polarization, specific heat [CRISMAT]).
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