Xiaoqin Chen

Although the internal field can effectively maintain the separation between photo-excited charge carriers, the wide bandgap restrains ferroelectric materials from visible light absorption. This study examined the effects of transition metal (TM) Mn, Fe, Co or Ni doping on the structure and bandgap of Bi _3.15 Nd _0.85 Ti ₃ O ₁₂ (BNdT) prepared by the molten salt synthesis method. No other non-bismuth layered structure phases were introduced. Mn, Co or Ni doping does not change the three-layered perovskite structure of BNdT while Fe doping increases the layer number from three to four. The doping of TM ions decreases the bandgap obviously. Among them, Mn-doped BNdT shows the largest bandgap reduction by ~1.6 eV. The narrowed bandgap was discussed to be attributed to the electronegativity of TM ions and the lattice distortion induced by doping together. The present work provides an available way to control the bandgap of complex oxide materials and provides a new tool for manipulating oxide optoelectronics.

Here, we use half-metallic Co2MnSi (CMS) ferromagnets to prepare CMS/Ag non-local lateral spin valve devices. By optimizing the structural property of CMS wires and the interface quality, device structure of CMS/Ag spin valves, large spin resistance about 4.2 mΩ can be observed clearly at room temperature when the gap length of two CMS wires is 200 nm. By fitting the spin accumulation signals, we obtained that the spin diffusion length for Ag wire is 290 nm and the spin polarization for CMS wires is 74%. These results indicate that half-metallic ferromagnetic materials can be used in semiconductor-based spin devices.