Magnetic interactions and magneto-electric coupling mechanisms in iron penta-halide hybrid compounds

Resumen del trabajo presentado al Joint JCNS-Workshop and Flipper: "Modern Trends in Neutron Scattering from Magnetic Systems and Single-Crystal Diffraction with Polarised Neutrons", celebrado en Tutzing (Alemania) del 3 al 7 de octubre de 2016.In magnetoelectric multiferroic materials, a subtle competition between different magnetic interactions is at the origin of multiferroicity, as this competition is the responsible of the formation of a magnetic structure able to induce ferroelectric polarization. The difficulty in controlling this interplay of interactions explains the scarce number of these materials report-ed. Recently, A2[FeCl5(H2O)] (A = Cs, K, Rb) have been identified as new linear magnetoe-lectric materials, while (NH4)2[FeCl5(H2O)] was established as a type II multiferroic, with strong magnetoelectric coupling and with a rich phase diagram upon application of magnetic field. The crystal and magnetic structures of (ND4)2[FeCl5(D2O)] and Cs2[FeCl5(D2O)] in different regions of their phase diagrams have been studied by neutron diffraction, trying to understand the mechanisms of magneto-electric coupling in these com-pounds. Spherical neutron polarimetry has been used to elucidate the occurrence of a collinear magnetic structure in a particular region of the phase diagram of (ND4)2[FeCl5(D2O)] and to determine the nature and population of the coexisting magnetic domains at 2K. 1D polarime-try (flipping ratio method) has been employed to obtain spin-density maps that could shed light on the magnetic interactions at the origin of the magnetic structures and, ultimately, of the magneto-electric coupling.Peer Reviewe