Magnetic-Field-Induced Change of Magneto-Electric Coupling in the in Molecular Multiferroic (ND4)2[FeCl5(D2O)]

摘要

Our results describe an unprecedented example of change in the mechanism ofmagnetically-induced electric polarization from spin current to spin-dependentp-d hybridization model. We have followed the evolution of the magneticstructures of (ND4)2[FeCl5 D2O] compound using single crystal neutrondiffraction under external magnetic field. The spin arrangements change fromincommensurate cycloidal to commensurate distorted-cycloidal and finally toquasi-collinear. The determination of the magnetic structures allows us toexplain the observed electric polarization in the different ferroelectricphases. Two different magneto-electric coupling mechanisms are at play: thespin-current mechanism for external magnetic field below 5 T, and the spindependent p-d hybridization mechanism for magnetic field above this value,being this compound the first example reported presenting this sequence ofmagneto-electric coupling mechanisms.