Liangliang Yin

Visible-light-driven photocatalysts: (La/Bi + N)-codoped NaNbO3 by first principles

To improve the photocatalytic activity of NaNbO3 for water splitting, the bandgap and the band edges of NaNbO3 should be tailored to match the visible part of the solar spectrum and hydrogen and oxygen redox potentials. By analyzing the band structures of La/Bi-doped and (La/Bi + N)-codoped NaNbO3, we found that the pseudointermediate band (PIB) was formed in the bandgap in all the doped systems because of the orbital splitting of the Nb 4d induced by the dramatically enlarged O-Nb-O angles. The PIB could make the wide bandgap semiconductors absorb visible-light photons as long as it was degenerate or partially degenerate. Considering that the appropriate band edges and absorption properties, we believe that (La/Bi + N)-codoped NaNbO3 materials are promising photocatalysts for hydrogen production through water splitting under visible-light irradiation without other modifications.

An investigation of the electronic properties of MgO doped with group III, IV, and V elements: trends with varying dopant atomic number

The electronic properties and the trends with varying dopant atomic number of III, IV, and V main group elements in MgO have been investigated using density functional theory. It is found that all of the geometry-optimized systems with the dopant atom replacing O in MgO exhibit half-metallic ferromagnetic properties regardless of metal or non-metal doping, and this agrees well with other theoretical computations. However, because of the high formation energy of metal atoms substituting for O atoms, we have calculated metal atom substitution for the Mg atom in MgO. We found that this system has a paramagnetic state and the formation energy is much lower than that of the former case. Finally, we have performed calculations for MgO doped with an F atom which shows a metallic behavior.

A facile method for effective doping of Tb3+ into ZnO nanocrystals

A technical challenging issue in rare-earth ion doping in ZnO nanocrystals has been tackled in this communication by a novel isocrystalline core-shell protocol, and the fabricated ZnO:Tb(3+)/ZnO core/shell nanocrystals showed efficient doping and excellent optical properties.

Enhanced temperature effect on magnetoresistance in Fe/Mo multilayers

We have observed an enhancement of the temperature effect on magnetoresistance (MR) in Fe/Mo multilayers with the increase of the Mo layer thickness. MR at the first antiferromagnetic maximum is large and insensitive to the temperature whereas at the third antiferromagnetic maximum it is small and relatively sensitive to the temperature. We found that the mean free path of the conduction electrons increased with the increase of the Mo layer thickness at a fixed temperature and it decreased very slightly with the increase of the temperature at a fixed Mo layer thickness. The interlayer coupling, similar to MR, also has an enhanced temperature effect with the increase of the Mo layer thickness. There is a scaling relationship between the temperature effect on saturation field Hs and MR, which suggests that the decrease of the interlayer coupling strength is responsible for the enhanced temperature effect on MR.

Effect of progressive substitution of Bi3+ by La3+ on the structural, magnetic, and transport properties of Bi0.6Ca0.4MnO3

Structural, magnetic, and electronic transport properties of Bi0.6−xLaxCa0.4MnO3 (0≤x≤0.6) manganites have been studied systematically. The parent compound exhibits robust charge ordered antiferrromagnetic (COAFM) phase with TCO∼293 K and AFM Neel temperature TN∼149 K. The sample with x=0.1 show a M(T) curve of “arch bridge” form between 142 and 253 K, which is attributed to the AFM peak embedded in the broad transition of the CO. For the middle doping samples (0.2≤x≤0.4), although the CO peaks disappear as a result of the suppression of the long range CO state, AFM superexchange coupling has been strengthened with the increasing of La doping level. The Bi0.1La0.5Ca0.4MnO3 sample shows interesting phenomena such as magnetization steps and magnetic memory effect. The resistivity of the samples exhibits insulating behavior in our measured temperature range for x≤0.4. While both x=0.5 and x=0.6 compounds exhibit metal–insulator transition. Furthermore, large low field magnetoresistance (MR) and hysteresis ap...

Noise suppression and sensitivity manipulation of magnetic tunnel junction sensors with soft magnetic Co70.5Fe4.5Si15B10 layer

The voltage noise characteristic and sensitivity of magnetic tunnel junction sensors are crucial for ultralow field detection. In this work, we used a soft magnetic material electrode Co70.5Fe4.5Si15B10 as a sensing layer to improve the sensitivity. Then, a bias field along the easy axis of a free layer was applied to improve the linearity and manipulate the sensitivity of magnetic tunnel junction sensors. More importantly, random telegraph noise was suppressed by the bias field, resulting in hysteresis-free performance. The highest sensitivity of 3.9%/Oe and the best field detectivity of 4.5 nT/√ Hz at 10 Hz without hysteresis have been achieved. The sensors showed excellent performance with CoFeSiB electrodes, indicating that it is an effective way to improve the performance of sensors by introducing the bias field.The voltage noise characteristic and sensitivity of magnetic tunnel junction sensors are crucial for ultralow field detection. In this work, we used a soft magnetic material electrode Co70.5Fe4.5Si15B10 as a sensing layer to improve the sensitivity. Then, a bias field along the easy axis of a free layer was applied to improve the linearity and manipulate the sensitivity of magnetic tunnel junction sensors. More importantly, random telegraph noise was suppressed by the bias field, resulting in hysteresis-free performance. The highest sensitivity of 3.9%/Oe and the best field detectivity of 4.5 nT/√ Hz at 10 Hz without hysteresis have been achieved. The sensors showed excellent performance with CoFeSiB electrodes, indicating that it is an effective way to improve the performance of sensors by introducing the bias field.