Multiple nanocrystalline rare-earth hexaborides La1−xBaxB6 have been synthesized via a single step solid-state reaction. The Ba doping effects on crystal structure, grain morphology, magnetic and optical absorption properties were investigated using XRD, FESEM, HRTEM, SQUID magnetometry and optical measurements. The results show that all the Ba-doped hexaborides crystallize in the CsCl-type single phase, indicating the Ba atoms occupied the lattice sites of LaB6. The optical absorption results indicate that the absorption valleys of LaB6 are red-shifted from 622 nm to 780 nm when the Ba doping content increases to x = 0.8. The first-principle calculation results reveal that Ba doping reduces the total kinetic energy of the electrons of LaB6, which lead to the absorption valleys moving toward a higher wavelength. Meanwhile, the band gap of BaB6 obtained from optical absorption is in good agreement with the theoretical calculation results. The magnetic measurements results showed that Ba doping lead to room-temperature ferromagnetism of LaB6 due to the different ionic radii of La3+ and Ba2+ causing intrinsic crystal defects, which is directly observed experimentally by HRTEM. This is the first time that we have found the tunable optical and ferromagnetic behavior of Ba doped nanocrystalline LaB6. Thus, nanocrystalline La1−xBaxB6, as multi-functional materials, should open up a new route to extend the optical and magnetic applications of LaB6 nanopowder.
Li Yang,Hao Wu,Wenfeng Zhang,Xun Lou,Zijian Xie,Xu Yu,Yuan Liu,Haixin Chang
Room temperature ferromagnetic semiconductors remain one of the most puzzling issues to be solved in tens of years. Nowadays, 2D ferromagnetic transition metal dichalcogenides (TMDCs) nanosheets attract continuous interest due to their exceptional electronic structure and properties. Here, it is identified that semiconducting 2H-phase MoTe 2 few/mono-layer mixed nanosheets present a room temperature ferromagnetic property with Curie temperature above 400 K, although the MoTe 2 bulk counterpart shows diamagnetic properties. The origin of such observed room temperature ferromagnetism is attributed to the combination of their structural defects including Te vacancies, disorders, and amorphous imperfections and edge-states caused by reduced dimensionality. Moreover, a distinct enhancement of ferromagnetic properties at room temperature is revealed by a non-magnetic Ta doping strategy. Such structural defects and edge-states modulated ferromagnetism offers a feasible strategy to search for more robust room temperature ferromagnetic TMDCs nanosheets, which is essential to explore novel electronic and spintronic devices where both carrier charge and spin freedom can be controlled.
危险品化学品经营许可证（带存储）