Heteroepitaxial growth of ferromagnetic MnSb(0001) films on Ge/Si(111) virtual substrates

Molecular beam epitaxial growth of ferromagnetic MnSb(0001) has been achieved on high quality, fully relaxed Ge(111)/Si(111) virtual substrates grown by reduced pressure chemical vapor deposition. The epilayers were characterized using reflection high energy electron diffraction, synchrotron hard X-ray diffraction, X-ray photoemission spectroscopy, and magnetometry. The surface reconstructions, magnetic properties, crystalline quality, and strain relaxation behavior of the MnSb films are similar to those of MnSb grown on GaAs(111). In contrast to GaAs substrates, segregation of substrate atoms through the MnSb film does not occur, and alternative polymorphs of MnSb are absent

Fermi-level depinning at metal/GaN interface by an insulating barrier

We have investigated Schottky contacts on GaN and observed that Fermi level pinning is dominant at the metal/GaN interface with a pinning factor of 0.23. A methodology to solve the problem by introducing a thin layer of MgO between the metal and the semiconductor is demonstrated here. It is observed that the insertion of a thin layer of the insulator prevents the metal wave-function penetration into the semiconductor band gap which in turn helps in the Fermi level depinning for GaN. We have particularly demonstrated the Fermi level depinning for ferromagnetic Schottky contact Fe and shown its usefulness for electrical spin injection and detection. The resistance-area product of an as deposited Fe/GaN contact is found to be too high for efficient spin injection and detection. It is improved considerably by using a 3 nm layer of MgO and the effective barrier height is reduced to 0.4 eV. We have further investigated the influence of low work function metal Gd and found it is possible to do barrier height engineering when deposited in conjunction with other metals. (C) 2013 Elsevier B.V. All rights reserved

Memory Elements Using Multiterminal Magnetoresistive Devices

We have theoretically designed and experimentally demonstrated a multiterminal lateral magnetoresistive device using electrical spin injection and detection in semiconductor, which can act as a memory array. The memory state is associated with the direction of the magnetization state. The state is read out from clear transition in current both in magnitude and direction depending on the relative magnetization direction. The current shows a plateau in varying magnetic field regions indicating stable magnetization direction due to differences in coercivity. The device characteristics are well explained in the framework of two-dimensional spin transport and spin-dependent tunneling. (C) 2013 The Japan Society of Applied Physic

Bacteriophage T4 regA protein binds to the Shine-Dalgarno region of gene 44 mRNA.

We have overproduced and purified wild type regA protein, a translational repressor encoded by bacteriophage T4. The repressor activity of the cloned regA protein has been tested on four known regA target genes (T4 genes: 44, 45, rpbA and regA) using in vitro coupled transcription-translation reactions. We have demonstrated the sensitivity of two additional T4 genes coding for alpha- and beta-glucosyltransferases to regA protein in vitro. The regA target site on the gene 44 messenger RNA has been identified through deletion analysis and RNase protection assays, using plasmids containing gene 44-lacZ fusions. The effect of regA protein on expression of 44P-beta-galactosidase fusion proteins was assayed in vitro, in coupled transcription-translation reactions. Analysis of deletion mutants of gene 44-lacZ localized the regA recognition region to between nucleotides -11 and +9 of the mRNA. RNase protection assays of g44-lacZ transcripts further defined the site of regA protein interaction to between nucleotides -10 and +2 of the mRNA. This region overlaps the gene 44 Shine-Dalgarno region and the A and U of the initiation codon

Modulation bandwidth of a spin laser

We have studied small signal frequency response of a spin laser. We have shown that the response is characterized by two distinct resonant peaks corresponding to the two polarization modes of the spin laser. It is observed that the modulation bandwidth of a spin laser can be smaller or larger than that of a conventional laser depending upon the current bias and spin relaxation time constant. A small value for spin relaxation constant may not be detrimental for modulation bandwidth. This anomalous observation is explained by considering both the amplitude and phase response of the two polarization modes. A spin laser can act as a combination of low-pass and bandpass filters. The passband frequency range is tunable by external bias. We have also studied the evolution of resonant peaks and modulation bandwidth as a function of spin relaxation time constant. (C) 2011 American Institute of Physics. [doi:10.1063/1.3556959

Enhanced magnetoresistance in lateral spin-valves

The effect of feature sizes on the characteristics of lateral spintronic devices have been investigated experimentally and theoretically. It is demonstrated that confining spin-transport in the active region of a device enhances magnitude of the spin-dependent response substantially. Numerical simulation of spin-transport corroborates the experimental observations. Device characteristics are found to be a strong function of spin-polarizer and analyzer dimensions. The response is observed to attain a peak value for an optimum device feature size, and this is seen to be a function of temperature. Spin dependent effects become weaker for very small and very large devices. (c) 2010 [doi:10.1063/1.3488818