X. G. Xu

Intrinsic room temperature ferromagnetism in boron-doped ZnO

We report room temperature ferromagnetism in boron-doped ZnO both experimentally and theoretically. The single phase Zn1−xBxO films deposited under high oxygen pressure by pulsed laser deposition show ferromagnetic behavior at room temperature. The saturation magnetization increases monotonically from 0 to 1.5u2002emu/cm3 with the increasing boron component x from 0% to 6.8%. The first-principles calculations demonstrate that the ferromagnetism in the B-doped ZnO originates from the induced magnetic moment of oxygen atoms in the nearest neighbor sites to B–Zn vacancy pairs. The calculated total magnetic moment shows an increasing trend with the boron component which is consistent with experiment.

Ionized-oxygen vacancies related dielectric relaxation in heteroepitaxial K0.5Na0.5NbO3/La0.67Sr0.33MnO3 structure at elevated temperature

Ferroelectric K0.5Na0.5NbO3 (KNN) thin film was epitaxially grown on La0.67Sr0.33MnO3 (LSMO) buffered LaAlO3 substrate by pulse laser deposition. The crystallographic structure of KNN/LSMO was confirmed by x-ray diffraction. Interestingly, a dielectric relaxor feature was found in the temperature range 200–350u2009°C. The activation energies for relaxation and conduction of the films were found to be 1.87 and 0.63–0.71 eV, respectively. The mechanism for dielectric relaxation in KNN/LSMO structure was discussed under a thermally activated process. The remnant polarization and coercive field of the films were 21.3u2002μC/cm2 and 91 kV/cm, respectively.

Ultra-thin BiFeO 3 nanowires prepared by a sol-gel combustion method: An investigation of its multiferroic and optical properties

Perovskite-type polycrystalline BiFeO3 nanowires, with 150xa0nm in length and 10xa0nm in diameter, were synthesized using a sol–gel combustion method at a relative low reactive temperature. The BiFeO3 nanowires exhibit a remarkably high saturation magnetization of 4.22 emu/g finite coercivity (177 Oe), and a enhanced Mr/Ms value about 0.22, which is independent on the synthesize temperature. The permittivity constant (ε′) and dielectric loss (0.01 at 0.4xa0MHz) of BiFeO3 nanowires are very low as compared to reported BiFeO3 bulk and film. In addition, BiFeO3 nanowires reveal a wide band gap of 2.5xa0eV measured from the UV–visible diffuse reflectance spectrum, which may be useful as a photoelectrode material and photocatalytic decomposition of contamination.

High-performance, low-operating voltage, and solution-processable organic field-effect transistor with silk fibroin as the gate dielectric

We report the use of silk fibroin as the gate dielectric material in solution-processed organic field-effect transistors (OFETs) with poly(3-hexylthiophene) (P3HT) as the semiconducting layer. Such OFETs exhibit a low threshold of −0.77u2009V and a low-operating voltage (0 to −3 V) compatible with the voltage level commonly-used in current electronic industry. The carrier mobility of such OFETs is as high as 0.21 cm2 V−1 s−1 in the saturation regime, comparable to the best value of P3HT-based OFETs with dielectric layer that is not solution-processed. The high-performance of this kind of OFET is related with the high content of β strands in fibroin dielectric which leads to an array of fibers in a highly ordered structure, thus reducing the trapping sites at the semiconductor/dielectric interface.

Anomalous Hall effect and spin-orbit torques in MnGa/IrMn films: Modification from strong spin Hall effect of the antiferromagnet

We report systematic measurements of anomalous Hall effect (AHE) and spin-orbit torques (SOTs) in MnGa/IrMn films, in which a single

Perpendicularizing magnetic anisotropy of full-Heusler Co2feAl films by cosputtering with terbium

L{1}_{0}text{ensuremath{-}}mathrm{MnGa}

Effect of Ta Underlayer on Perpendicular Anisotropy of TbFeCo Films

epitaxial layer reveals obvious orbital two-channel Kondo (2CK) effect. As increasing the thickness of the antiferromagnet IrMn, the strong spin Hall effect (SHE) has gradually suppressed the orbital 2CK effect and modified the AHE of MnGa. A scaling involving multiple competing scattering mechanisms has been used to distinguish different contributions to the modified AHE. Finally, the sizeable SOT in the MnGa/IrMn films induced by the strong SHE of IrMn have been investigated. The IrMn layer also supplies an in-plane exchange bias field and enables nearly field-free magnetization reversal.

Enhanced ferroelectric and UV photocatalytic properties in a Bi4Ti3O12@ZnO core–shelled nanostructure

In this letter, we fabricated Co2FeAl films with perpendicular-to-plane magnetic anisotropy by cosputtering with terbium (Tb). The as-prepared (Tb+Co2FeAl) films (TCFA) consists of nanocrystalline L21 Co2FeAl and amorphous alloy of Tb(Co, Fe, and Al). The coercivity field (Hc) of the TCFA films is adjustable from 200 to 800 Oe. After annealing, the Hc decreases to 70 Oe. A perpendicularly magnetized spin valve with the TCFA films as free and reference layers shows a current-perpendicular-to-plane magnetoresistance of 1.8% at room temperature. Our result opens a way to fabricate perpendicularly magnetized full-Heusler alloys and makes it possible to realize faster and simple structured magnetic storage bits in the future.

Organic field-effect transistors with a low driving voltage using albumin as the dielectric layer

We study Ta underlayer thickness dependence of perpendicular magnetic anisotropy (PMA) in TbFeCo films. The experiment shows that perpendicular coercivity, saturation magnetization, and remanent squareness ratio of the TbFeCo films change significantly with the Ta underlayer thickness. For example, the perpendicular coercivity (Hc) of the films increases from 671 to 2305 Oe. The reason is that the Ta underlayer affects the number of magnetic pinning sites and the oxidation of the films by residual oxygen atoms in the experimental environment.

Improved electrical and ferroelectric properties of multiferroic Na0.5Bi0.5TiO3/Bi1.07Nd0.03FeO3/Na0.5Bi0.5TiO3 sandwiched structure by a sol–gel process

Composited Bi4Ti3O12@ZnO nanoparticles with a core of Bi4Ti3O12 (BIT) and a shell of ZnO have been synthesized by liquid chemical reaction method. Compared with pure BIT nanoparticles, the ferroelectricity in BIT@ZnO core–shell nanostructure was greatly enhanced. Moreover, the dielectric loss of BIT@ZnO is lower than that of BIT nanoparticles in a low frequency range. The band gap energy of BIT@ZnO core@shell nanostructure is larger than that of BIT, which formed as a type-II band alignment. Furthermore, the BIT@ZnO core–shell nanoparticles exhibit better UV photodegradation activity for organic contaminant. Such a BIT@ZnO core@shell nanostructure may have potential applications in microelectronics, photoelectronic, and photocatalytic of contamination.