Room‐temperature Magnetocapacitance Spanning 97K Hysteresis in Molecular Material

Abstract Magnetic capacitor, as a new type of device, has broad application prospects in fields such as magnetic field sensing, magnetic storage, magnetic field control, power electronics and so on. Traditional magnetic capacitors are mostly assembled by magnetic and capacitive materials. Magnetic capacitor made of a single material with intrinsic properties is very rare. This intrinsic property is magnetocapacitance (MC). The studies on MC effect have mainly focused on metal oxides so far. No study was reported in molecular materials. Herein, two complexes: (CETAB) 2 [CuCl 4 ] ( 1 ) and (CETAB) 2 [CuBr 4 ] ( 2 ) (CETAB=(2‐chloroethyl)trimethylammonium) are reported. There exist strong H−Br and Br−Br interactions and other weak interactions in complex 2 , so the phase transition energy barrier is high, resulting in the widest thermal hysteresis loop on a molecular level to date. Furthermore, complexes 1 and 2 show large MC parameters of 0.247 and 1.614, respectively, which is the first time to observe MC effect in molecular material.