Designing of a Magnetodielectric System in Hybrid Organic-inorganic framework, a Perovskite Layered Phosphonate MnO3PC6H4-m-Br.H2O
Résumé
Very few hybrid organic–inorganic framework (HOIF) exhibit direct coupling between spins and dipoles and are also restricted to a particular COOH-based system. It is shown 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 the 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 ≈20 K followed by weak ferromagnetic ordering below 12 K (T1) with a magnetic field (H)-induced transition ≈25 kOe below T1. All these magnetic features are exactly captured in the T and H-dependent dielectric constant, ε′(T) and ε′(H). This demonstrates direct magnetodielectric coupling in this designed hybrid and yields a new path to tune multiferroic ordering and magnetodielectric coupling.