Shu-qin Xiao

Giant magnetoimpedance effect in sandwiched films

The giant magnetoimpedance (GMI) effect in films with a sandwiched structure has been studied. FeNiCrSiB/Cu/FeNiCrSiB sandwiched films with a magnetic closed-loop structure were deposited onto a glass substrate by rf sputtering and then annealed at an optimum temperature. GMI ratios as large as 63% and 77% were obtained at 13 MHz in longitudinal and transverse fields, respectively. The ratios are almost twice as large as those obtained in FeNiCrSiB single films.

Magnetic properties and giant magneto-impedance in amorphous FeNiCrSiB films

The giant magneto-impedance effect has been observed at room temperature in amorphous FeNiCrSiB films prepared by RF sputtering followed by an annealing treatment. The frequency spectra and field dependence of the effect are studied in the frequency range from 100 kHz to 13 MHz and the magnetic field range from 0 to 70 Oe. The longitudinal, transverse and perpendicular effects are observed in detail. A transverse magneto-impedance effect with a magnitude similar to the longitudinal case has been obtained, and a large perpendicular MI effect is also obtained. A maximum GMI ratio of about 38% is obtained at 13 MHz in the longitudinal and transverse cases. The field sensitivity of the longitudinal GMI is 3.4% at 13 MHz. A large perpendicular MI ratio of 11% is obtained at 11 MHz. The effect of annealing on the effective permeability and GMI is reported in this paper.

Magnetic Properties and Giant Magneto-Impedance in Nanocrystalline FeCuCrVSiB Films

The giant magneto-impedance (GMI) effect has been observed in nanocrystalline FeCuCrVSiB films prepared by rf sputtering followed by an annealing treatment. The magnetic properties and the longitudinal and transverse GMI have been studied in detail. Field dependence and frequency spectra of GMI effect have been studied in the frequency range from 100 kHz to 13 MHz. Maximum GMI ratios as large as 50% and 25% were obtained at 13 MHz in the longitudinal and transverse cases, respectively. The field sensitivity of the longitudinal GMI is about 0.11% m/A at 13 MHz. The dependence of effective permeability on the frequency and magnetic field has been investigated.

Effect of hydrogenation on transport and magnetic properties in homogeneous amorphous MnxGe1−x:H films

Homogeneous amorphous MnxGe1−x:H films were synthesized under thermal nonequilibrium condition by magnetron co-sputtering technology with hydrogen in Ar atmosphere. Compared to the MnxGe1−x films without hydrogen, the MnxGe1−x:H films with hydrogen show higher concentration of hole carriers, larger conductivity, and higher saturation magnetization. Moreover, it was found that the anomalous Hall resistivity is proportional to the perpendicular magnetization. These electrical and magnetic properties indicate that the ferromagnetism of the MnxGe1−x:H films is intrinsic ferromagnetism mediated by the spin-polarized hole carriers.

The giant-magneto-impedance effect in FM/Ag/FM (FM≡FeCuCrVSiB) sandwich films

Sandwich films with the structure FM/Ag/FM have been prepared by radio-frequency sputtering and then annealed at an optimized temperature (here FM represents the FeCuCrVSiB amorphous soft magnetic layer). The giant-magneto-impedance (GMI) effects for the samples have been studied as a function of alternating-current frequency (50 kHz to 13 MHz) and external magnetic field. When the frequency increases above a critical frequency f* (about 150 kHz), the GMI ratio increases quickly with increasing frequency, and reaches a maximum value at a characteristic frequency fm of about 4 MHz. GMI ratios at fm as large as 109% and 135% were obtained for longitudinal and transverse applied magnetic fields, respectively. These results are much better than those obtained for single-layer films, and the frequencies used in producing the effect are very low.

Rashba spin–orbit coupling enhanced anomalous Hall effect in MnxSi1−x/SiO2/Si p–i–n junctions

Rashba spin–orbit coupling, which allows the manipulation of electron spins in semiconductor heterostructures, has attracted great interest due to its potential applications in spintronic devices. But it is still not clear whether the Rashba spin–orbit coupling in a p–n junction can have a significant effect on the anomalous Hall effect of a p-type ferromagnetic semiconductor film grown on an n-type semiconductor substrate. Here MnxSi1−x/SiO2/Si p–i–n junctions were formed by sputtering p-type MnxSi1−x magnetic semiconductor films on near-intrinsic n-type Si substrates with about 1 nm SiO2 native oxide layer. Although Mn0.48Si0.52/SiO2/Si p–i–n junctions and Mn0.48Si0.52 magnetic semiconductor films grown on insulating glass substrates almost show the same positive anomalous Hall effect at low temperature below 150 K, Mn0.48Si0.52/SiO2/Si p–i–n junctions show a greatly enhanced negative anomalous Hall effect around the temperature of 200 K. On further analysis of the in-plane resistance of Mn0.48Si0.52 films and the I–V curves of the p–i–n junctions, the enhanced negative anomalous Hall effect is attributed to the interfacial Rashba spin–orbit coupling in Mn0.48Si0.52/SiO2/Si p–i–n junctions.

Giant Magneto-Impedance Effect in As-Deposited Multilayered Amorphous Films

Giant magneto-impedance effects have been observed in as-deposited amorphous FeCuNbSiB/Cu/FeCuNbSiB and FeCuNbSiB/SiO2/Ag/SiO2/FeCuNbSiB multilayered films. The films were deposited onto Si substrates by radio frequency sputtering. In FeCuNbSiB/Cu/FeCuNbSiB films, maximum giant magneto-impedance ratios as large as 32% and 11% were obtained at 13 MHz in the longitudinal and transverse fields, respectively. In FeCuNbSiB/SiO2/Ag/SiO2/ FeCuNbSiB films, the maximum giant magneto-impedance ratios were 47% and 57% at the same frequency for the two cases, which are much larger than those obtained in the annealed single layer films.

Domain structure and giant magneto-impedance effect in FeCuNbSiB films prepared with a magnetic field

Domain structure and giant magneto-impedance(GMI) effects of FeCuNbSiB films,which were prepared by radio frequency sputtering without field and with a magnetic field about 72 kA/m,are investigated.The results show that after annealing at 300°C,the GMI ratios reach the maximum values of about 38% in longitudinal and 27% in transverse dc magnetic fields,at a frequency of 13 MHz.The longitudinal magnetic responses of GMI ratios show very sharp peaks around the transverse anisotropy field,and the sensitivity can reach 47.5%/kA m?1 in the field range 0.4-6 kA/m,at 13 MHz.The transverse anisotropy is 0.4 kA/m,larger than that of 0.08 kA/m in the film prepared without magnetic field,because an additional transverse anisotropy is induced by the field applied in the fabrication process.

Structure, band gap, and Mn-related mid-gap states in epitaxial single crystal (Zn1−xMgx)1−yMnyO thin films

Epitaxial (Zn1−xMgx)1−yMnyO thin films were grown on c-Al2O3 substrates by radio frequency oxygen plasma assisted molecular beam epitaxy. Single crystal structure of the (Zn1−xMgx)1−yMnyO films was revealed by reflection high energy electron diffraction and X-ray diffraction. The band gap of the films can be tuned dramatically with increasing the Mg concentration, while the onset energy of Mn-related mid-gap absorption band only shows a small blue shift. Photoconductivity measurements indicate the Mn-related mid-gap states in (Zn1−xMgx)1−yMnyO films can create free carriers and contribute to charge transfer transitions. The conduction band offset ΔEC = 0.13 eV and valence band offset ΔEV = 0.1 eV were obtained for ZnO/Zn0.8Mg0.2O heterostructures, which increase to ΔEC = 0.21 eV and ΔEV = 0.14 eV for ZnO/Zn0.7Mg0.3O heterostructures.