Giant Magnetoelectric Coupling and Magnetic-Field-Induced Permanent Switching in a Spin Crossover Mn(III) Complex

Abstract

We investigate giant magnetoelectric coupling at a Mn 3+ spin crossover in [Mn III L]BPh4 (L = (3,5-diBr-sal)2323) with field-induced permanent switch of the structural, electric and magnetic properties. An applied magnetic field induces a 1 st order phase transition from a high spin/low spin (HS-LS) ordered phase to a HS-only phase at 87.5 K that remains after the field is removed. We observe this unusual effect for DC magnetic fields as low as 8.7 T. The spin-state switching driven by the magnetic field in the bistable molecular material is accompanied by a change in electric polarization amplitude and direction due to a symmetry-breaking phase transition between polar space groups. The magnetoelectric coupling occurs due to a γη 2 coupling between the order parameter γ related to the spin-state bistability, and the symmetry-breaking order parameter η, responsible for the change of symmetry between polar structural phases. We also observe conductivity occurring during the spin crossover, and evaluate the possibility that it results from conducting phase boundaries. We perform ab-initio calculations to understand the origin of the electric polarization change as well as the conductivity during the spin crossover. Thus we demonstrate a giant magnetoelectric effect with a field-induced electric polarization change that is 1/10 of the record for any material.

Domain Wall Dynamics in a Ferroelastic Spin Crossover Complex with Giant Magnetoelectric Coupling

“…In Figure 7 b we show that the electric polarization Δ P also undergoes a field-induced jump with a magnetic field as low as 4 T. All of the different structural states of this material are polar and can be expected to have different electric polarizations, as was also observed in the Br analogue of this compound. 68 A key point is that, due to the ferroelastic transition, the electric polarization, which is confined in the ( a , c ) plane in the monoclinic HT and INT2 phases, gets a component along the b axis in the INT1 and LT triclinic phases. We expect a change in electric polarization at every structural phase transition, and the temperature-dependent electric polarization is shown in Figure S17 in the Supporting Information.…”

Magnetic Field Perturbations to a Soft X-ray-Activated Fe (II) Molecular Spin State Transition

“…Currently, magneto-electric coupling is being explored in oxides, and raises increasing interest because magneto-electric and multiferroic materials are seen as a pathway to voltage-controlled nonvolatile logic [3,4] and memory [4]. There are few investigations of magneto-electric coupling in molecular systems, with clear demonstrations now provided for [Mn 3+ (taa)] (H 3 taa = tris(1-(2-azolyl)-2-azabuten-4-yl) amine) [5,6], and [Mn 3+ (3,5-diBr-sal) 2 323)]BPh 4 [7], which undergo a spin state transition; these have recently been accompanied by a complementary theory [7,8]. Magneto-electric coupling has also been observed in single crystals of NiCl 2 -4SC(NH 2 ) 2 [9].…”

Thermal and Magnetic Field Switching in a Two‐Step Hysteretic MnIII Spin Crossover Compound Coupled to Symmetry Breakings

“…SCO and its coupled properties [20, 21, 25] can be influenced and switched by external stimuli including temperature, light, pressure, electric and magnetic fields [2, 3, 24, 26] . Compared to temperature, parameters such as electric and magnetic fields can allow for more rapid and/or improved control of material manipulation and are pursued for this reason [25] .…”

“…To date, magnetic‐field‐induced SCO have mostly only been observed at high fields above 30 T, which limits the accessibility of these transitions [10, 24, 33] . Examples of compounds that show magnetic‐field‐induced SCO behaviour below 14 T, which are accessible by typical superconducting magnets, are extremely rare [21, 23] . In the few reported cases, the lower field‐induced transitions can be observed just below the critical temperature of the cooperative SCO.…”