Magnetic excitations of the hybrid multiferroic (ND4)2FeCl5·D2<

High-Field Magnetoelectric and Spin-Phonon Coupling in Multiferroic (NH4)2[FeCl5·(H2O)]

“…23 Modeling of the inelastic neutron scattering reveals that J 2 and J 4 are the sources of frustration and responsible for the cycloidal character of the spin waves. 25 Numerical simulation shows that in-plane magnetic anisotropies as well as geometrical frustration in the exchange interactions stabilize the collinear sinusoidal phase. 31 (NH 4 ) 2 [FeCl 5 •(H 2 O)] is a type II system.…”

“…Molecule-based materials offer these opportunities in abundance. They retain many of the same physical characteristics as the oxides while offering lower energy scales, tunable chemical architectures, flexible lattices, and rich phase diagrams. − This makes molecule-based multiferroics like [(CH 3 ) 2 NH 2 ]­Mn­(HCOO) 3 , Cu­(CH 3 ) 2 SOCl 2 , and Cu­(pyz)­(gly)­ClO 4 superb platforms for exploring unique states of matter away from equilibrium. ,− Others including κ-(BEDT-TTF) 2 Cu­[N­(CN) 2 ]Cl and NiCl 2 –4SC­(NH 2 ) 2 are wholly molecular in nature with through-space intermolecular interactions that provide both electric and magnetic functionality. , In this work, we build upon recent magnetization and neutron scattering on multiferroic (NH 4 ) 2 [FeCl 5 ·(H 2 O)] − with a combination of high field electric polarization, magneto-infrared spectroscopy, and first-principles lattice dynamics calculations. By so doing, we provide a framework for understanding the interplay between charge, structure, and magnetism in this system.…”

“…(NH 4 ) 2 [FeCl 5 ·(H 2 O)] displays a series of temperature-driven transitions (Figure c) including an order–disorder transition at 79 K; magnetic ordering of the S = 5/2 Fe 3+ centers below T N = 7.25 K that creates a collinear sinusoidal spin wave structure with K = (0, 0, 0.23) and ferroelectricity below T FE = 6.9 K that arises due to the development of an incommensurate-cycloidal spin state K 1 = (0 0 0.23) that coexists (and competes) with a commensurate distorted cycloidal phase K 2 = (0 0 0.25) . Modeling of the inelastic neutron scattering reveals that J 2 and J 4 are the sources of frustration and responsible for the cycloidal character of the spin waves . Numerical simulation shows that in-plane magnetic anisotropies as well as geometrical frustration in the exchange interactions stabilize the collinear sinusoidal phase .…”

“…The strength of each pathway is indicated. These values are determined from fits to the neutron scattering data …”

“…Weak interactions between the H centers of the ammonium counterion and the Cl and O ions are also present. ,, We employ a single J Hamiltonian, and the negative sign indicates antiferromagnetic interactions. The in-plane anisotropy D is 0.17 K . (c) Summary of temperature- and field-driven transitions.…”