Designing of a magnetodielectric system in hybrid organic-inorganic framework, a perovskite layered phosphonate MnO3PC6H4-m-Br.H2O

Abstract: The research on multiferrocity and magnetoelectric coupling in metal-organic system is rare. Very few hybrid organic-inorganic frameworks (HOIF) exhibit direct magnetoelectric coupling (coupling between spins and dipoles) and also restricted to particular COOH-based system. We show how one can design a hybrid system to obtain such coupling based on the rational design of the organic ligands. The layered phosphonate, MnO3PC6H5.H2O, consisting of perovskite layers stacked with organic phenyl layers, is used as a starting potential candidate. To introduce dipole moment, a closely related metal-phosphonate, MnO3PC6H4-m-Br.H2O is designed. For this purpose, this phosphonate is prepared from 3-bromophenylphosphonic acid that features one electronegative bromine atom directly attached on the aromatic ring in meta position, lowering the symmetry of precursor itself. Thus, bromobenzene moieties in MnO3PC6H4-m-Br.H2O induce a finite dipole moment. This new designed compound exhibits complex magnetism, as observed in layered alkyl chains MnO3PCnH2n+1.H2O materials, namely, 2D magnetic ordering around 20 K followed by weak ferromagnetic ordering below 12 K(T1) with a magnetic field (H)-induced transition around 25 kOe below T1. All these magnetic features are exactly captured in T and H-dependent dielectric constant, epsilon(T) and epsilon(H). This demonstrates direct magnetodielectric coupling in this designed hybrid and yields a new path to tune multiferroic ordering and magnetodielectric coupling.