S.M. Liu

Fabrication of La0.8Na0.2Mn1−xCuxO3 (x = 0, 0.05) thin films on YSZ substrates via chemical solution deposition

a-Axis oriented La0.8Na0.2MnO3 (LNMO) and La0.8Na0.2Mn0.95Cu0.05O3 (LNMCO) films with large magnetoresistance (MR) near room temperature are fabricated via chemical solution deposition on yttrium-stabilized zirconia (YSZ) (1 0 0) single crystal substrates. With slight Cu doping, it is found that the growth mode is changed from the layer-by-layer mode of the LNMO film to the island mode of the LNMCO film. The LNMO film exhibits typical transport properties of epitaxial films of manganites. However, the LNMCO film shows transport properties corresponding to polycrystalline films of manganites. The MR value of the LNMCO film at low applied magnetic field is also remarkably enhanced compared with that of the LNMO film below the insulator–metal transition temperature. MR as high as 9% is obtained at a field of 0.05 T at 5 K. The enhanced MR effect for the LNMCO film is attributed to the spin-dependent scattering of polarized electrons at the grain boundaries.

Investigations of helium incorporated into a film deposited by magnetron sputtering

Helium-containing titanium film was prepared by magnetron sputtering in a gas mixture of helium and argon. This method distinctly differs from traditional helium introduction into metals. A high concentration of helium up to 45 at.% and a uniform distribution in the bulk were shown by ion beam analysis. The process of helium incorporation is considered in which the helium particles are energetically backscattered from the target, fly through the glow discharge zone and are consequently embedded into the growing film. It is virtually a continuous sub-threshold-energy implantation during film deposition based on the plasma technique. The limited partial pressure of argon is to maintain the discharge and sputter the titanium target. The helium content incorporated can be controlled conveniently by adjusting the pressure of the working gases. X-ray diffraction, transmission electron microscopy, Doppler broadening of positron beam analysis and thermal helium desorption spectroscopy revealed the microstructure of titanium films, the state of helium bubbles, the defect characteristic related to helium and thermal release behaviour of helium from the titanium film.

Photon-assisted magnetophonon resonance in a GaAs/AlGaAs heterojunction driven by intense terahertz radiations

Abstract The DC magnetoresistivity of a two-dimensional semiconductor under an intense electromagnetic radiation of THz frequency, is studied using a balance-equation approach for terahertz-driven magnetotransport. We find that, for a radiation field of frequency around 1 THz and amplitude of order of 1 kV/cm, the longitudinal resistivity of a GaAs heterojunction, as a function of the cyclotron frequency ωc of the magnetic field, exhibits distinct peaks related to zero-, one- and two-photon emission and absorption processes, and the overall shape of the resistivity curve changes greatly due to the irradiation.