Magnetoelectric Radical Hydrocarbons

Abstract

macroscopically characteristic state in bulk assemblies (high-temperature molecular magnet, superconductor, etc.). Recent investigations of molecular radicals have mainly concentrated on the exchange interaction involving s and p orbitals. For a pair of correlated electrons in different orbitals, the net spin (S) can be either 0 (antiparallel spins) or 1 (parallel spins), corresponding to the singlet and triplet states, which can attribute to the anti-ferromagnetic (AFM) or ferromagnetic (FM) spin coupling. [4][5][6] If such significant coupling can be maintained in a crystalline extended bulk structure, molecular radical magnets with high Curie or Neel temperature could be achievable. Although considerable progress has been made in the preparation of molecular radical magnets, the design of all-molecular radical magnetoelectric materials (RMEs) has remained elusive. [8][9][10][11][12] The prominent magnetoelectric mechanisms of organics include the spin and charge order-driven ferroelectricity in quantum anti-ferromagnetic compounds. [12][13][14] The RMEs provide an efficient method for the mutual control of radical magnetism and electric dipoles. The coupling between the magnetic and the electric orders generates novel functionalities, which do not exist in either single state. [8,9,[15][16][17] In recent years, there has been an enormous effort to discover new classes of polycyclic aromatic hydrocarbons (PAHs) with two or more functionalities, for example, magnetism [3][4][5] and conductivity, [18] ferroelectricity and optoelectronics, [19,20] which is partially associated with complex charge transfer and radical interactions. The relationship between magnetic order characteristics and charge order has rarely been studied in PAHs, which is distinctly different from the typical ME effect in inorganic materials, [12,15] especially the inorganic single solid phase with magnetoelectric effect. [21,22] Radical magnetic interactions in PAHs rely on the competition between the spins of unpaired electrons and thermal motion, and therefore, diradicals with magnetic exchange interactions are particularly relevant as they are comparable to thermal energy kT within the available temperature range. In addition, utilization of charge transfer and radical PAHs with large visible-light absorption is a promising route toward photoconductance and photovoltaic applications. [23] Here we investigate potassium-doped radical terphenyl (K 1.5 C 18 H 14 ) PAH with bulk anti-ferromagnetic spin coupling and ferroelectric imidazolium perchlorate (ImClO 4 ) compound RME solids, where the K atom is between two C 18 H 14 layers along the a-axis direction for the herringbone structured The molecular radicals, systems with unpaired electrons of open-shell electronic structures, set the stage for a multidisciplinary science frontier relevant to the cooperative magnetic exchange interaction and magnetoelectric effect. Here ferroelectricity together with magnetic spin exchange coupling in molecular radical hydrocarbon solids is reported, repres...

Room‐Temperature Magnetoelectric Response in Molecular–Ionic Ferroelectric‐Based Magnetoelectric Composites

“…As far as we know, this is the first example of a molecular–ionic ferroelectric‐based magnetoelectric composite to realize a giant magnetoelectric response (8.74 V Oe −1 cm −1 ). The value is clearly larger that of K 1.5 C 18 H 14 /imidazolium perchlorate (converse magnetoelectric effect: 2.9 V Oe −1 cm −1 ) and is comparable with that of some magnetoelectric composites, such as the typical Terfenol‐D/Pb(Mg 1 / 3 Nb 2 / 3 )O 3 –PbTiO 3 (10.3 V Oe −1 cm −1 ), and Metglas/Pb(Zr,Ti)O 3 (7 V Oe −1 cm −1 ) . Although the magnetoelectric effect of Metglas/ 1 is still weaker than that of Metglas/Pb(Mg 1/3 Nb 2/3 )O 3 –PbTiO 3 (1100–7000 V Oe −1 cm −1 at the resonance frequency) and Metgals/PVDF copolymer (238–383 V Oe −1 cm −1 at the resonance frequency),[5a,11,14] the performance of the molecular ferroelectric‐based magnetoelectric composite materials will promote quickly with the evolution of molecular ferroelectric.…”

Inorganic–Organic Hybrid Molecular Materials: From Multiferroic to Magnetoelectric

“…[110,111] In addition, Ren et al reported the photovoltaic effects and converse ME response of the all-molecular radical ME material ImClO 4 /K 1.5 C 18 H 14 (ImClO 4 is the room-temperature molecular ferroelectric imidazolium perchlorate and K 1.5 C 18 H 14 is the potassium-doped radical terphenyl). [112] Because K 1.5 C 18 H 14 shows bulk antiferromagnetic spin coupling rather than ferromagnetism, no direct ME response is expected for the ImClO 4 /K 1.5 C 18 H 14 composite. Recently, we prepared a laminated ME composite based on the molecular-ionic ferroelectric [N(CH 3 ) 4 ][GaBrCl 3 ] and amorphous FeBSi alloy (Metglas).…”

Organic radical ferroelectric crystals with martensitic phase transition

“…In pursuit of biocompatibility and light weight, organic multi-functional ferroelectric materials are highly desirable for smart medicine and wearable electronics 7 , 8 . Organic radicals are attractive building blocks for achieving multifunctionality since they usually exhibit hysteretic responses to external stimuli 9 , 10 . 2,2,6,6-Tetramethylpiperidine- N -oxyl (TEMPO) is well-known as a stable single-component radical compound 11 .…”