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In order to acquire a soft magnetic film with low conductivity and large magnetic anisotropy, the strain-modulated magnetic anisotropy is studied in epitaxial MgFe2O4 (MFO) films. The MFO films with thicknesses of 25, 48, 75, and 110 nm are grown on the MgAl2O4 (MAO) (100) substrate using a pulsed laser deposition technique. Due to the large lattice-mismatch (3.34%) between MFO and MAO substrates, the interface exhibits a large tetragonal compressive strain. The results of field-dependent magnetization suggest the soft magnetic nature of all the measured MFO films. The analysis of angular dependent ferromagnetic resonance reveals the large uniaxial magnetic anisotropy energy (Ku) of −1.62 × 106 erg/cm3 in the highly strained 25 nm film, and Ku decreases with the increasing thickness due to strain relaxation. The observed large magnetic anisotropy in these highly strained MFO thin films is larger than most of the soft ferrite thin films, which arise due to tetragonal distortion and inverse magnetostriction. The epitaxial MFO thin films with enhanced magnetic anisotropy could be one of the potential candidates for spin filters. [ABSTRACT FROM AUTHOR]

Pt Schottky contacts on (001)-orientated Nb-doped SrTiO3 (NSTO) in both ambient air and vacuum were investigated by the conductive atomic force microscope. The co-existed TiO2 and SrO termination layers were identified on the terrace-structured NSTO surface, where the former possessed a higher forward current than the latter. In ambient air, the barrier height of Pt/NSTO Schottky junction exhibited periodical variation with cyclic terrace plane and step sites, whereas it became homogeneous in ambient vacuum. We suggested that the oxygen absorption and releasing of surface dangling bonds were the origin for reversible changes in transport properties, which indicates a feasible approach for the surface modulation and band structure tailoring of NSTO based heterojunctions. [ABSTRACT FROM AUTHOR]

Critical analysis on the magnetic properties of synthetic ferrimagnet (SyF), Ta/MgO/CoFeB/Ru/ CoFeB/MgO/Ta, is demonstrated via both static and dynamic techniques. With the Ru thickness being 2.3 nm, the coupling between two CoFeB layers becomes orthogonal, which can be used for spin-transfer-torque nano-oscillator (STNO). The fitting of angular dependent ferromagnetic resonance (FMR) allows the precise determination of magnetic anisotropy of each CoFeB layer, the relative magnetizations and the exchange field near the frequency of STNO applications. In addition, the mechanism of resonance broadening at out-of-plane direction is identified to be magnetic inhomogeneity by fitting the angular dependent linewidth of FMR spectra, which provides indispensable information for the future design of STNO devices. [ABSTRACT FROM AUTHOR]

In this paper, Ag/Bi0.9La0.1FeO3 (BLFO)/La0.7Sr0.3MnO3 sandwich structure was grown epitaxially on SrTiO3 substrates using pulsed laser deposition. Short-circuit photocurrent (Ishort) and frequency dependence of the capacitance were investigated. It reveals that this heterostructure exhibits strong photocurrent responses, the orientation of Ishort depends strongly on the polarization orientations, and it varies monotonically from one orientation to the other as the polarization orientation switching gradually from upward (downward) to downward (upward), the Ishort value becomes zero when the film is in zero polarization states. The intensity of the Ishort can be strengthened by several times after thousands of bipolar electric pulses. Moreover, after polarization fatigue process of bipolar electric pulses or under light illumination, the capacitance of this sandwich structure is always bigger than the original state. However, the magnifying ratio of the capacitance after and before polarization fatigue process or under light illumination decrease with increasing the frequency in the C-f curves. These results suggest that polarization induced surface charge combined with migration of oxygen vacancies is the primary driving force for the varying of interfacial barriers and the oxygen vacancies density near the interface, which in turn leads to different orientations and values of Ishort as well as the differential interfacial capacitance. Our results indicate that the photovoltaic response in ferroelectric BLFO thin films could be further explored for solar light photovoltaic and other capacitor devices applications. [ABSTRACT FROM AUTHOR]

We include the effect of band non-parabolicity on photonic defect states within the Wannier theory, which improves the quadratic approximation adopted by Painter et al. [Phys. Rev. B 68, 035214 (2003)] for large-size defects, as well as extends the theory to a wider range of defect size. A 2D hexagonal photonic crystal is considered, and analyzed for the origin and degree of non-parabolicity in the 1st TE band around J-point, and for the effect of non-parabolicity on acceptor type cavity modes. The non-parabolicity is shown to derive primarily from the inherent anisotropy of band dispersion around the point. Overall, with the inclusion of non-parabolicity, (i) mode degeneracy is lowered, (ii) the 'binding energy' of a cavity mode is increased, and (iii) the cut-off of defect size for a given cavity mode is reduced, by as much as 35% in certain cases, in comparison with that calculated without the non-parabolicity. A simple 'overall effective mass' picture is provided for the understanding of non-parabolicity effects. [ABSTRACT FROM AUTHOR]

The oxygen vacancies in the SrTiO3 (STO) single crystal with two different cap layers, CoFe2O4 (CFO) and BiFeO3 (BFO), are investigated with the technique of electron paramagnetic resonance (EPR). EPR spectra show the resonance lines of the residual oxygen vacancy in air annealed STO, STO/CFO, and STO/BFO, showing the high sensitivity of EPR to the low concentration defects. The experimental results indicate that the oxide cap layers enhance the oxygen deficiency in bulk STO and the amount of oxygen vacancy is dependent on the electronegativity of metal ion in the cap layer. Accordingly, STO/BFO has a larger amount of oxygen vacancy than that of STO/CFO. [ABSTRACT FROM AUTHOR]

We present an approach for electrically manipulating nuclear spins in n-GaAs using an on-chip microcoil. Optically injected spin-polarized electrons are used to generate a dynamic nuclear polarization via electron-nucleus hyperfine interaction with a characteristic time constant of ∼10 min. The saturated Overhauser field amplitude is on the order of several 10 mT and proportional to the spin polarization degree of the injected electrons. Applying an rf field resonant for the 75As nuclei, complete depolarization of 75As nuclear spins is observed. [ABSTRACT FROM AUTHOR]

We have synthesized a series of LuMn1-xFexO3 (0⩽x⩽0.2) samples and study the effect of Fe-doping on their magnetic and dielectric properties. The magnetic characterization indicates that with increasing Fe-content up to 0.2, the antiferromagnetic (AFM) transition temperature increases from 90 to 105 K. A corresponding shift in the peak-positions of specific heat and dielectric anomaly is observed, indicating a strong correlation between the magnetic ordering and the electric polarization. Further analysis suggests that the rising of AFM transition temperature with increasing Fe-content should be from the structural origin, in which the strength of AFM interaction as well as the electrical polarization is dependent on the in-plane lattice parameters. [ABSTRACT FROM AUTHOR]

Multiferroic composites of NiFe2O4 (NFO) and BiFe0.5Cr0.5O3 (BFCO) are synthesized and their dielectric, magnetic, and magnetoelectr)ic (ME) properties are measured at room temperature. NFO-BFCO forms a two-phase composite. The composite has a larger magnetization and dielectric constant than those of both parent compounds, due to the effects of interfacial strain on BFCO. Furthermore, the ME response in NFO-BFCO is about one time larger than that of BFCO, revealing the success of magnetic control of the dielectric response via the mechanical coupling, which can be exploited in the future applications of multiferroic composites. [ABSTRACT FROM AUTHOR]

Magnetization reversal phenomena in submicron half-ring patterned wires with different corner structures have been investigated. The wires with corner structures of rectangular, semicircle, and triangular shapes were connected in series by two or five half-rings. The variation of domain structures with magnetic field is illustrated by electron transport measurements, simulation, and magnetic force microscopy (MFM) images. The switching behavior depends on the corner structures connecting the half-ring structures. These results are consistent with the domain pattern and magnetic phase shift observation provided by the MFM measurements. [ABSTRACT FROM AUTHOR]

Domain wall pinning force in the junctions (corners), with different shapes of square, semicircle, or triangle, of half-ring in-series wires is considered to study the current injection induced wall movements. This geometry has less thermal activation at the region of domain wall nucleation in contrast to notch structures. The wires with square corners have the largest domain pinning force to resist polarized current-induced magnetization reversal, judging from the largest slope in the current-field dependence (ΔI/ΔH=0.274). [ABSTRACT FROM AUTHOR]