Origin of ferromagnetism in Sm-doped In2S3 nanoparticles: Experimental and theoretical insights

Diluted magnetic semiconductors with room-temperature ferromagnetism (RTFM) opens new prospects for the development of next-generation spintronic devices. For now, the rare earth doping is an effective method to tune the ferromagnetism of semiconductor materials. In this work, we fabricated undoped In₂S₃ and In₂S₃: Sm³⁺ nanoparticles using gas-liquid phase chemical deposition method. UV-visible and photoluminescence spectra demonstrate that the introduction of Sm³⁺ ions lead to bandgap narrowing and enhanced luminescence intensity. Magnetic characterizations show that all synthetic samples display a ferromagnetic behaviour, and the maximum saturation magnetization of the samples can be tuned by regulating the concentration of doped Sm³⁺ ions. The RTFM in Sm doped In₂S₃ nanoparticles derives from the coupling interaction between the localized defect states and Sm³⁺ ions and is described using bound magnetic polarons (BMPs) mechanism. First-principle calculations reveal that In vacancies and Sm dopants are responsible for the generation of magnetic moments which come mainly from S 3p orbitals around the In vacancy and Sm 4f orbitals. Our results suggest that In₂S₃: Sm³⁺ nanoparticles constitute promising semiconductor materials for use in future electronic and spintronic devices.