Multiferroic Semiconducting Behavior in Quasi-2D Cu-Based Hybrid Perovskites

Developing multifunctional materials is crucial for overcoming the limitations of conventional technological scaling. Intrinsic multiferroic semiconductors are especially attractive because they integrate magnetic, ferroelectric, and semiconducting functionalities within a single material. Here, we demonstrate the intrinsic multiferroic semiconducting behavior and ligand tunability in two quasi-two-dimensional (2D) organic–inorganic hybrid perovskites, (C7H9NBr)2CuX4 (X = Cl, Br). Ferromagnetism arises from Cu2+ ions, while the 4-bromobenzylammonium spacer breaks the inversion symmetry, generating ferroelectricity. Long-range magnetic order emerges below 10 and 15 K for the Cl and Br analogs, respectively, corroborated by the heat capacity anomalies and low-temperature magnon contributions. Both compounds exhibit room-temperature ferroelectricity, establishing them as type-I multiferroics. Transport measurements reveal hole mobilities of ∼10–4 cm2 V–1 s–1, comparable to those of 2D perovskite semiconductors. Furthermore, the photoinduced dielectric enhancement across the full frequency range highlights their optoelectronic potential. These results expand the family of intrinsic multiferroic semiconductors and provide a platform for realizing multifunctional properties.