The effect of the dopant Y on high-pressure-induced polymorph transformation was investigated in Ag2S nanocrystals.

Searching for the polymorphic semiconductor nanocrystals would provide precise and insightful structure-spin polarization correlations and meaningful guidance for designing and synthesizing high spin-polarized spintronic materials. Herein, the high spin polarization is achieved in polymorphic CdS:Y semiconductor nanocrystals. The high-pressure polymorph of rock-salt CdS:Y nanocrystals has been recovered at ambient conditions synthesized by the wurtzite CdS:Y nanocrystals as starting material under 5.2 GPa and 300 °C conditions. The rock-salt CdS:Y polymorph displays more robust room-temperature ferromagnetism than wurtzite sample, which can reach the ferromagnetic level of conventional semiconductors doped with magnetic transition-metal ions, mainly due to the significantly enhanced spin configuration and defect states. Therefore, crystal structure directly governs the spin configuration, which determines the degree of spin polarization. This work can provide experimental and theoretical methods for designing the high spin-polarized semiconductor nanocrystals, which is important for applications in semiconductor spintronics.

We use first-principles calculations to investigate the mechanism of the effect of native defects on the spin polarization and exchange coupling interaction in the V 3 O 4 semimetal material. Our results reveal that, in contrast to other neutral defects, V vacancy defects in V 3 O 4 at A/B sites are in favor of higher spin polarization degrees and lower defect formation energies. Compared to ideal V 3 O 4 , the V vacancy defects at A/B sites cause slightly lower spin polarization degrees but much higher exchange coupling interactions. Our results suggest an effective route to mediate the spin polarization and exchange coupling by defect engineering, which promotes the applications of the V 3 O 4 semimetal material in spintronics.

Room-temperature ferromagnetic wurtzite CdS:Y semiconductor nanocrystals have been fabricated via an effective doping atomization method. The atomization is in favor of the Y 3+ cations entering into the host CdS lattice.

There is an urgent need for a complete understanding of intrinsic ferromagnetism, due to the necessity for application of ferromagnetic semiconductors. Here, further insight into the magnetic mechanism of sulfur antisite-induced intrinsic high-temperature ferromagnetism is investigated in Ag2S:Y nanocrystals. The gas-liquid phase chemical deposition method is adopted to obtain the monoclinic Ag2S:Y nanocrystals. The field and temperature-dependent magnetization measurements demonstrate the robust high-temperature ferromagnetism of Ag2S:Y nanocrystals. As revealed in the magnetic origin study from first-principles calculations, the intrinsic sulfur antisite defect is only responsible for the creation of a magnetic moment which mainly comes from the S 3p and Ag 4d orbitals. Such a mechanism, which is essentially different from those of dopants and other native defects, provides new insight into the origin of the magnetism.