Doping-Concentration-Induced Ferromagnetism and Antiferromagnetism in In2S3:Dy3+ Quantum Dots

Diluted magnetic semiconductor (DMS) quantum dots have been researched extensively due to their potential applications in next-generation spin-based devices. Herein, the cubic In2S3:Dy3+ DMS quantum dots (3-5 nm) with different doping concentrations were synthesized via a gas-liquid phase chemical deposition method. The effect of Dy3+ content on the photoluminescence (PL) and ferromagnetism was investigated. The PL emission spectra exhibit a blue-shift compared with those reported previously due to the increased quantum size confinement and enhanced intensity attributed to the Dy3+ doping. The distinct and stronger room-temperature ferromagnetism is observed from vibrating sample magnetometer (VSM) measurement. The coexistence of ferromagnetic (FM) and antiferromagnetic (AFM) phases and antiferromagnetic interation plays a dominant position after a certain doping concentration value can be further confirmed according to the zero field cooling/field cooling (ZFC/FC) curves. As revealed in the magnetic origin study from first-principles calculations, the ferromagnetism obtained arises not only from the Dy atoms but also from the In vacancies. In addition, we also proposed a spontaneous mechanism based on the bound magnetic polaron theory to explain the change of saturation magnetizations along with Dy3+ doping concentration. This work provides experimental and theoretical guidance for designing and synthesizing unique spintronic materials, which can promote development of spintronic applications.