Reversible Thermochromism and Strong Ferromagnetism in Two‐Dimensional Hybrid Perovskites

Abstract

Two‐dimensional (2D) hybrid perovskites have shown many attractive properties associated with their soft lattices and multiple quantum well structure. Herein, we report the synthesis and characterization of two new multifunctional 2D hybrid perovskites, (PED)CuCl4 and (BED)2CuCl6, which show reversible thermochromic behavior, dramatic temperature‐dependent conductivity change, and strong ferromagnetism. Upon temperature change, the (PED)CuCl4 and (BED)2CuCl6 crystals exhibit a reversible color change between yellow and red‐brown. The associated structural changes were monitored by in situ temperature‐dependent powder X‐ray diffraction (PXRD). The (BED)2CuCl6 exhibits superior thermal stability, with a thermochromic working temperature up to 443 K. The conductivity of (BED)2CuCl6 changes over six orders of magnitude upon temperature change. The 2D perovskites exhibit ferromagnetic properties with Curie temperatures around 13 K.

Structural Features in Some Layered Hybrid Copper Chloride Perovskites: ACuCl4 or A2CuCl4

“…The susceptibility (χ) is plotted as a function of T during field cooling in Figure 7. The magnetic properties of all three compounds reveal features similar to previously reported 2D layered copper(II) perovskites, 25,43,44 viz., long-range ferromagnetic interactions within the [CuCl 4 ] ∞ layers. The similar ferromagnetic behaviors in related layered Cu 2+ perovskites, and also that of the related J-T active Mn 3+ , have been quantified Aguado et al 45 In that work, key structural parameters were associated with ferromagnetic behavior (viz.…”

“…These kinds of properties also make Cu-based halide perovskites sensitive to pressure and temperature. Pressure-induced changes in electronic, magnetic, and optical properties of Cu-based halide perovskites have been studied intensively, not only providing intriguing properties but also permitting insights into their structure–property relationships. − …”

Polarity and Ferromagnetism in Two-Dimensional Hybrid Copper Perovskites with Chlorinated Aromatic Spacers

“… 43 The band gaps obtained from Tauc plots ( Figure 9 ) are about 2.43 eV for (2-ClbaH) 2 CuCl 4 , 2.28 eV for (3-ClbaH) 2 CuCl 4 , and 2.25 eV for (4-ClbaH) 2 CuCl 4 , accompanied by a small regulative magnitude of 0.18 eV, which are comparable to that observed in other perovskites, e.g., 2.48 eV for (CH 3 NH 3 ) 2 CuCl 4 11 and 2.16 eV for (BED) 2 CuCl 6. 16 The interoctahedral distortions of the inorganic framework play an important role in determining the band gap of layered hybrid halide perovskites. 44 The two polar compounds (3-ClbaH) 2 CuCl and (4-ClbaH) 2 CuCl 4 possess narrower band gaps, in agreement with their smaller interoctahedral distortions (larger Cu–Cl–Cu angles; Table 2 ).…”

Synthesis, growth, and characterisation of a novel organic–inorganic perovskite-type hybrid system based on glycine

“…Actually, the compound showed significantly hard distortion in the level of the co-ordination spheres CdCl6 giving rise to changes in the Cd-Cl bond lengths and alternation of long and short bonds ( Cd-Cl). As known, the magnitude of the distortion of the octahedron has an effect on the intensity of the super-exchange interaction between ion, further leading to a weak or a strong ferromagnetism [44]. x 10 -4 emu.g -1 .…”