Jakobsen Vibe B, Chikara Shalinee, Yu Jie-Xiang, Dobbelaar Emiel, Kelly Conor T, Ding Xiaxin, Weickert Franziska, Trzop Elzbieta, Collet Eric, Cheng Hai-Ping, Morgan Grace G, Zapf Vivien S
School of Chemistry, University College Dublin, Belfield, Dublin 4, Dublin, Ireland.
National High Magnetic Field Lab, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States.
Inorg Chem. 2021 May 3;60(9):6167-6175. doi: 10.1021/acs.inorgchem.0c02789. Epub 2020 Dec 17.
We investigate giant magnetoelectric coupling at a Mn spin crossover in [MnL]BPh (L = (3,5-diBr-sal)323) with a field-induced permanent switching of the structural, electric, and magnetic properties. An applied magnetic field induces a first-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 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.
我们研究了[MnL]BPh（L = (3,5 - 二溴 - 水杨醛)323）中锰自旋交叉处的巨磁电耦合，其结构、电学和磁学性质可通过场诱导实现永久切换。施加的磁场在87.5 K时诱导了从高自旋/低自旋（HS - LS）有序相到仅高自旋相的一级相变，且在磁场移除后该相变依然存在。我们观察到，对于低至8.7 T的直流磁场，这种不寻常的效应依然存在。在双稳态分子材料中，由磁场驱动的自旋态切换伴随着极化幅度和方向的变化，这是由于极性空间群之间的对称破缺相变引起的。磁电耦合是由于与自旋态双稳性相关的序参量γ和负责极性结构相之间对称性变化的对称破缺序参量η之间的γη耦合而产生的。我们还观察到自旋交叉过程中出现的电导率，并评估了其由导电相边界导致的可能性。我们进行了从头算计算，以了解自旋交叉过程中极化变化以及电导率的起源。因此，我们展示了一种巨磁电效应，其场诱导的极化变化是任何材料记录值的1/10。
