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Spin–orbit-induced (SOI) field of crystalline GaMnAs ferromagnetic film has been investigated by using planar Hall effect measurements. The presence of SOI field manifested itself as an asymmetry in the magnetization reversal process between positive and negative current directions. A significant Joule heating caused by current has been observed and its effect was carefully considered to obtain the magnetic anisotropy of the GaMnAs film. The switching of magnetization by SOI field in the GaMnAs film was demonstrated in the absence of an external field. [ABSTRACT FROM AUTHOR]

Interlayer exchange coupling (IEC) between ferromagnetic (FM) metal Fe and FM semiconductor GaMnAs has been investigated by using magnetotransport measurements. The realization of diverse magnetization alignments, including collinear and non-collinear configurations, between Fe and GaMnAs layers are observed during the magnetization reversal process measured by the planar Hall effect. Minor loop scan reveals the presence of FM IEC between Fe and GaMnAs, which systematically decreases as the temperature increases. [ABSTRACT FROM AUTHOR]

We report a method for accurate determination of the strength of the current-induced spin-orbit (SO) field in ferromagnetic GaMnAs films. The SO-field manifests itself in the form of a hysteresis between planar Hall resistances (PHR) measured with positive and negative currents as an applied magnetic field is rotated in the sample plane at constant field strength. The width of the hysteresis, which is related to the strength of the SO-field, is observed to change significantly for different values of the rotating external field strength. Since the SO field occurring at a given current is an intrinsic property of the crystal, such a field dependence of the hysteresis indicates that the width of the hysteresis measured with a single field strength is insufficient for determining the SO field. However, using a model based on magnetic free energy that includes the effects of magnetic anisotropy and the SO-field as developed in the present paper, we show that the SO field for a given current density can be accurately established by fitting to the experimentally observed dependence of transition angles of PHR measured with different applied field strengths. Using the known dependence of magnetic anisotropy of GaMnAs on temperature, we also show that this method applies reliably as the temperature varies. [ABSTRACT FROM AUTHOR]

We report a systemeatic investigation of magnetic anisotropy of quaternary GaMnAsP ferromagnetic semiconductor films by magneto-transport. Hall measurements showed a transition of the easy magnetization direction from in-plane to out-of plane with incorporation of the P into the GaMnAs films. Quantitative information on magnetic anisotropy of the films is obtained by fitting the angular dependence of Hall resistance data to magnetic free energy using the coherent rotation model. Values of magnetic anisotropy parameters show that in-plane anisotropy decreases and out-ofplane anisotropy increases with increasing P content in these films. The out-of-plane magnetic anisotropy in GaMnAsP layers is further enhanced by low temperature annealing. By optimizing the growth and annealing conditions, we were able to obtain a Curie temperature of 125 K in such quaternary films, with strong out-ofplane anisotropy. This study showed that the magnetic anisotropy of the GaMnAsP films can be controlled by adjusting the concentration of the P, and by appropriate post-growth annealing. [ABSTRACT FROM AUTHOR]

We have investigated the magnetic properties of the Ni films deposited on a GaAs and a Bi2Se3 buffer grown by molecular beam epitaxy on a GaAs (001) substrate. The magnetization measurements at 4 K revealed that the coercivity of the Ni films decreases monotonically with increasing thickness up to 25 nm in both cases. However, the coercivity measured at 4 K was always larger in the Ni film deposited on the surface of Bi2Se3 than in the film deposited on the GaAs. Such enhancement of the coercivity decreases with increasing temperature and film thickness. This suggests that the Bi2Se3 surface alters the magnetic properties of the Ni film. The increase of the coercivity was more serious in an un-capped Ni/Bi2Se3 sample, which showed an exchange bias effect due to the oxidation of the top surface of the Ni film. These observations are important for the investigation of spin dependent phenomena in magnetic systems involving a ferromagnet/topological insulator interface. [ABSTRACT FROM AUTHOR]

Magnetic anisotropy of Fe films grown on (001) GaAs substrates using Ge buffer layers were investigated by planar Hall effect measurements. In addition to phenomena arising from dominant cubic symmetry of the Fe specimen, the study of angular dependence of magnetization reversal revealed breaking of this symmetry in the form of systematic asymmetric shifts of magnetic hysteresis loops around the < 110 > crystallographic directions. We ascribe such symmetry breaking to an admixture of uniaxial anisotropy associated with the [100] direction in the Fe film. To determine the parameters associated with this uniaxial anisotropy, we quantitatively analyze the asymmetric shifts of the hysteresis loop centers from the < 110 > directions. Even though the value of these parameters turns out to be relatively small compared to that of the cubic anisotropy (by about two orders of magnitude), they survive up to room temperature. [ABSTRACT FROM AUTHOR]

Antibody-conjugated gold nanorods (GNRs) have been used for the targeting and imaging of specific cancer markers expressed on the surface membrane of cancer cells. GNRs with various aspect ratios were fabricated, and their surface-enhanced Raman scattering enhancement effects were evaluated. To attach the GNRs selectively onto the targets in cancer cells, specific antibodies were immobilized on the surface of GNRs using the layer-by-layer deposition method. First, Raman reporter molecules, mercaptopyridine, were attached to the surface of GNRs, and their surface charge was modified using poly(sodium 4-styrene-sulfonate) to make the surface charge negative. Then, anti-rabbit IgGs were immobilized onto the surface of the GNRs by electrostatic interactions. HER2 markers, expressed on the cell surface, were treated with anti-HER2 primary antibodies. Finally, the functionalized nanoprobes, conjugated with secondary antibodies, were attached to the markers on cancer cells by antibody–antibody interactions. In the present study, MCF7 cells overexpressing breast cancer marker HER2 were used as the optical imaging targets. Our experimental results demonstrate the potential feasibility of antibody-conjugated GNRs for the highly sensitive targeting and imaging of biomarkers expressed on the surface membrane of cancer cells. [ABSTRACT FROM AUTHOR]

High-pressure electroosmotic pumps (EOPs) operate on the principle that electroosmotic flow (EOF) can be generated through a packed-bed capillary by applying an electric field through it. In this paper, a novel packed-bed EOP design using nanosilica particles is described. The packed-bed capillary was fabricated using a capillary of 5 cm x 530 mum i.d. close packed with silica particles having an average particle size of 20-30 nm. The flow rates, pressures and pressure/flow rate (P-Q)characteristics, electric properties of the pump and the influence of phosphate buffer concentration on the pump were carefully studied. By increasing the pressure, decreasing the applied voltage, and the electric current, the thermodynamic efficiency was about 1%-2% for inorganic buffers and 3%-5% for organic solvents or their mixture without ions. [ABSTRACT FROM PUBLISHER]

Our investigation of thin GaMnAs films with different thicknesses revealed that the magnetic properties of this material strongly depend on film thickness. For this study, a single GaMnAs film was selectively etched, and its properties were then investigated by planar Hall effect measurements. A particularly important conclusion from the results is the emergence of a uniaxial anisotropy field along the [100] crystalline direction, which increases rapidly with increasing film thickness. We argue that such thickness dependence of the [100] uniaxial anisotropy results from the crystal structure of the film, rather than from the effects of the interface between the GaMnAs and the substrate. [ABSTRACT FROM AUTHOR]

Magnetoresistance in antiferromagnetically coupled GaMnAs/GaAs:Be multilayers exhibits a unique step feature caused by sequential flips of magnetization in individual GaMnAs layers. Hysteresis loops corresponding to such magnetization flips in specific layers were measured by adjusting the range of the field scan to where the flip occurs. Using the hysteresis shifts of such partial loops, we were able to obtain the strength of the interlayer exchange coupling exerted on a given GaMnAs layer by the rest of the multilayers. This also allowed us to quantitatively establish the magnitude of the coupling of each GaMnAs layer with its adjacent neighbors. [ABSTRACT FROM AUTHOR]

Magnetization reversal in a GaMnAs film grown on a Si substrate was investigated using planar Hall effect measurements. The angular dependence of the planar Hall resistance (PHR) shows that cubic crystalline anisotropy along the directions dominates the film’s magnetic anisotropy. However, the magnetization reversal behavior varies significantly with the applied field strength: as the magnetic field strength decreases, the PHR amplitude decreases, and hysteresis appears in data obtained with clockwise and counterclockwise rotation of the field directions. Furthermore, asymmetry in the PHR amplitude between the two opposite field directions appears during the angle scan and increases with decreasing field strength. We show that these features arise from a broad distribution of magnetic domains having different pinning fields. [ABSTRACT FROM AUTHOR]