Giant Magnetoresistance Research Papers - Academia.edu (original) (raw)
For Abstract see ChemInform Abstract in Full Text.
"The room-temperature crystal structure of the brownmillerite SrCaMnGaO5+d (d ¼ 0:035) has been refined from neutron powder diffraction data; space group Ima2, a ¼ 15:7817ð6Þ; b ¼ 5:4925ð2Þ, c ¼ 5:3196ð2ÞA( . Mn and Ga occupy 99.0(2)%... more
"The room-temperature crystal structure of the brownmillerite
SrCaMnGaO5+d (d ¼ 0:035) has been refined from neutron
powder diffraction data; space group Ima2, a ¼ 15:7817ð6Þ;
b ¼ 5:4925ð2Þ, c ¼ 5:3196ð2ÞA( . Mn and Ga occupy 99.0(2)% of
the 6- and 4-coordinate sites, respectively. A combination of
magnetometry, neutron diffraction and lSR spectroscopy has
shown that the compound orders magnetically at 180 K, and that
the low-temperature phase has a G-type antiferromagnetic
structure, with an ordered magnetic moment of 3.30(2) lB per
Mn at 2K. Displaced hysteresis loops provide evidence that the
atomic moment has an additional, glassy component. Magnetometry
shows that significant short-range magnetic interactions
persist above 180 K, and lSR that the spin fluctuations are
thermally activated in this temperature region. The compound is
an electrical insulator which at 159K shows an unusually large
magnetoresistance of 85% in 6T, increasing to 90% in
13 T."
Research in semiconductor spintronics aims to extend the scope of conventional electronics by using the spin degree of freedom of an electron in addition to its charge. Significant scientific advances in this area have been reported, such... more
Research in semiconductor spintronics aims to extend the scope of conventional electronics by using the spin degree of freedom of an electron in addition to its charge. Significant scientific advances in this area have been reported, such as the development of diluted ferromagnetic semiconductors, spin injection into semiconductors from ferromagnetic metals and discoveries of new physical phenomena involving electron spin. Yet no viable means of developing spintronics in semiconductors has been presented. Here we report a theoretical design that is a conceptual step forward-spin accumulation is used as the basis of a semiconductor computer circuit. Although the giant magnetoresistance effect in metals has already been commercially exploited, it does not extend to semiconductor/ferromagnet systems, because the effect is too weak for logic operations. We overcome this obstacle by using spin accumulation rather than spin flow. The basic element in our design is a logic gate that consists of a semiconductor structure with multiple magnetic contacts; this serves to perform fast and reprogrammable logic operations in a noisy, room-temperature environment. We then introduce a method to interconnect a large number of these gates to form a `spin computer'. As the shrinking of conventional complementary metal-oxide-semiconductor (CMOS) transistors reaches its intrinsic limit, greater computational capability will mean an increase in both circuit area and power dissipation. Our spin-based approach may provide wide margins for further scaling and also greater computational capability per gate.
Microwave-radiation induced giant magnetoresistance oscillations recently discovered in high-mobility two-dimensional electron systems in a magnetic field, are analyzed theoretically. Multiphoton-assisted impurity scatterings are shown to... more
Microwave-radiation induced giant magnetoresistance oscillations recently discovered in high-mobility two-dimensional electron systems in a magnetic field, are analyzed theoretically. Multiphoton-assisted impurity scatterings are shown to be the primary origin of the oscillation. Based on a model which considers the interaction of electrons with the electromagnetic fields in Faraday geometry, we are able not only to reproduce the correct period, phase and the negative resistivity of the main oscillation, but also to obtain secondary peaks and additional maxima and minima in the resistivity curve, some of which were already observed in the experiments.
A series of FeCo–SiO2 nanogranular films were prepared using magnetron controlled sputtering method. The microstructure, tunneling giant magnetoresistance (TMR) and magnetic properties of FeCo–SiO2 films deposited at room temperature and... more
A series of FeCo–SiO2 nanogranular films were prepared using magnetron controlled sputtering method. The microstructure, tunneling giant magnetoresistance (TMR) and magnetic properties of FeCo–SiO2 films deposited at room temperature and then annealed at various temperatures were investigated using transmission electron microscopy (TEM), conventional four probes method and vibrated sample magnetometer (VSM) under room temperature, respectively. The results showed that all FeCo–SiO2 films consisted of FeCo granules with equiaxial shape uniformly dispersed in the SiO2 matrix and formed body-centered cubic (bcc) structure. With increasing the annealing temperature, FeCo granule size increased monotonically. For film with 30.5vol% FeCo, the size distribution satisfied the log-normal function at lower annealing temperature. While with increasing annealing temperature, the size distribution deviated gradually from the log-normal function. Meanwhile, upon varying the annealing temperature, the TMR of films with lower volume fraction reached a peak value at higher annealing temperature and the TMR of films with higher volume fraction reached a peak value at lower annealing temperature. In addition, the results also indicated that the sensitivity of TMR changed non-monotonically with the increment of the annealing temperature and both the saturation magnetization and the susceptibility of FeCo (30.5vol%)–SiO2 films increased with increasing the annealing temperature.
The authors report on fabrication and characterization of a polymeric spin valve with the conjugated polymer regioregular (poly 3-hexylthiophene) (RRP3HT) as the spacer layer. The device structure is La0.67Sr0.33MnO3 (LSMO)/polymer/Co,... more
The authors report on fabrication and characterization of a polymeric spin valve with the conjugated polymer regioregular (poly 3-hexylthiophene) (RRP3HT) as the spacer layer. The device structure is La0.67Sr0.33MnO3 (LSMO)/polymer/Co, with half-metallic, spin-polarized LSMO acting as the spin-injecting electrode. The spin valve shows behavior similar to a magnetic tunnel junction though the nonmagnetic spacer layer (∼100 nm) is much thicker than the tunneling limit. They attribute this behavior to the formation of a thin spin-selective tunneling interface between LSMO and RRP3HT caused by RRP3HT, chemically attaching to LSMO as observed by x-ray photoelectron spectroscopy measurement. This gives rise to ∼80% magnetoresistance (MR) at 5 K and ∼1.5% MR at room temperature. They found that by introducing monolayer of different organic insulators between LSMO and RRP3HT the spin-selective interface is destroyed and the spin injection is reduced. Their results show that organic materials are promising candidates for spintronic applications.
Small magnetoresistive spin valve sensors (2×6 μm2) were used to detect the binding of single streptavidin functionalized 2 μm magnetic microspheres to a biotinylated sensor surface. The sensor signals, using 8 mA sense current, were in... more
Small magnetoresistive spin valve sensors (2×6 μm2) were used to detect the binding of single streptavidin functionalized 2 μm magnetic microspheres to a biotinylated sensor surface. The sensor signals, using 8 mA sense current, were in the order of 150–400 μV for a single microsphere depending on sensor sensitivity and the thickness of the passivation layer over the sensor surface. Sensor saturation signals were 1–2 mV representing an estimated 6–20 microspheres, with a noise level of ∼10 μV. The detection of biomolecular recognition for the streptavidin-biotin model was shown using both single and differential sensor architectures. The signal data compares favourably with previously reported signals for high numbers of magnetic microspheres detected using larger multilayered giant magnetoresistance sensors. A wide range of applications is foreseen for this system in the development of biochips, high sensitivity biosensors and the detection of single molecules and single molecule interactions.