Inorganic–organic hybrid switchable dielectric materials with the coexistence of magnetic anomalies induced by reversible high-temperature phase transition

Abstract

An inorganic–organic hybrid compound that features a zero-dimensional inorganic structural framework, N-methylpiperidinium tetrabromoferrate(III) (compound 1, [C₆H₁₄N][FeBr₄]), has been reported as a new switchable dielectric material with the coexistence of weak magnetic anomalies. It is noteworthy that 1 demonstrates remarkable dielectric responses, which can be tuned between two distinct dielectric states and reversibly switched by phase transition at ∼340 K (T_c). Its high-dielectric constants are at least 4 times as large as that of the low-dielectric state. Structural analysis reveals that 1 belongs to the monoclinic crystal system with the space group P2₁/c at room temperature, but transforms into an orthorhombic system with the space group Cmcm above T_c. The disordering of organic cations affords a driving force for high-temperature phase transition in 1 along with its switchable dielectric activities. Besides, weak magnetic anomalies were also found in 1 at the vicinity of its T_c, which should be reminiscent of another possible physical channel to the phase transition. This finding suggests that 1 might be a potential multifunctional material with the coexistence of switchable dielectric bistability and magnetic responses, which opens up new possibilities to develop molecular functional materials.