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A SiO2 cantilever covered by elliptical magnetic thin films was designed as an actuator. Under magnetic field, the elliptical magnetic film with sharp ends would exhibit single-domain structures and generate torque to push or pull the two arms of the cantilever. The cantilever could then stretch or compress and the displacement could be controlled by adjusting the magnitude and direction of the external magnetic field. The combination between micromagnetism of patterned films and actuator was successfully demonstrated. The magnetic actuator can be applied for future application in the biological field and would be valuable for microelectromechanical systems (MEMS). [ABSTRACT FROM AUTHOR]

We report on the structural and magnetic properties of CoFe2O4 films under epitaxial strain. The films are grown with high structural quality on MgO, SrTiO3, and piezoelectric Pb(Mg1/3Nb2/3)0.72Ti0.28O3 substrates by pulsed laser deposition. The substrate-induced strain is found effective to alter the magnetic anisotropy of the films. Reversible strain measurements using the piezoelectric substrates are providing evidence that nearly bulk-like magnetoelastic properties are maintained for films of down to at least 25nm thickness. This is in contrast to unsubstituted cobalt ferrite films and suggests that a chemical control of the spinel lattice provides a promising route to optimize the tunability of the magnetic properties of thin ferrite films. [ABSTRACT FROM AUTHOR]

The dramatically enhanced polarizations and saturation magnetizations observed in the epitaxially constrained BiFeO3 (BFO) thin films with their pronounced grain-orientation dependence have attracted much attention and are attributed largely to the constrained in-plane strain. Thus, it is highly desirable to directly obtain information on the two-dimensional (2D) distribution of the in-plane strain and its correlation with the grain orientation of each corresponding microregion. Here the authors report a 2D quantitative mapping of the grain orientation and the local triaxial strain field in a 250 nm thick multiferroic BFO film using a synchrotron x-ray microdiffraction technique. This direct scanning measurement demonstrates that the deviatoric component of the in-plane strain tensor is between 510-3 and 610-3 and that the local triaxial strain is fairly well correlated with the grain orientation in that particular region (22 References).

We present a study of the synthesis of epitaxial V2O3 films on c-plane Al2O3 substrates by reactive dc-magnetron sputtering. The results reveal a temperature window, at substantially lower values than previously reported, wherein epitaxial films can be obtained when deposited on [0001] oriented surfaces. The films display a metal-insulator transition with a change in the resistance of up to four orders of magnitude, strongly dependent on the O2 partial pressure during deposition. While the electronic properties of the films show sensitivity to the amount of O2 present during deposition of the films, their crystallographic structure and surface morphology of atomically flat terraced structures with up to micrometer dimensions are maintained. The transition temperature, as well as the scale of the metal-insulator transition, is correlated with the stoichiometry and local strain in the films controllable by the deposition parameters. [ABSTRACT FROM AUTHOR]

Epitaxial La0.67Ba0.33Ti0.02Mn0.98O3 (denoted as LBTMO hereafter) thin films of approximately 95 nm thickness were deposited by a pulsed laser deposition technique onto SrTiO3 (STO) (001) substrates. High-resolution X-ray diffraction (HRXRD) and transmission electron microscopy (TEM) investigations revealed that the films are epilayers with a four-fold symmetry around the [001] direction. Cross-sectional TEM and the presence of Pendellosung fringes in the XRD profiles demonstrate smooth interfaces. The STO substrate induces an in-plane compressive strain, which leads to a slight tetragonality of the film structure. The epilayers exhibit paramagnetic-to-ferromagnetic phase transitions at the Curie temperature TC (286 K), close to room temperature. The magnetization easy axis lies in the film plane along the [100] direction of the (001) substrate. The magnetic entropy change (ΔSM) associated with the second-order magnetic phase transition was determined via magnetization measurements in the temperature range between 210 and 350 K under different magnetic fields. The relative cooling power (RCP) of this film is about 220 J kg−1, somewhat lower than that of bulk Gd (410 J kg−1) for a 50 kOe field change, making the LBTMO ferromagnetic thin films a promising candidate for micro/nanomagnetic refrigeration around room temperature. The proposed universal curve provides a simple method for extrapolating ΔSM in a wide range of fields and temperatures, thus confirming the order of the magnetic transition in this system. The magnetic entropy (ΔSM)max around TC is proportional to (μ0H/TC)2/3 in agreement with the mean-field theory, indicating the existence of long-range ferromagnetic interactions in epitaxial LBTMO thin films. [ABSTRACT FROM AUTHOR]

Electrical and optical studies of defect structure of HgCdTe films grown by molecular beam epitaxy (MBE) are performed. It is shown that the peculiarity of these films is the presence of neutral defects formed at the growth stage and inherent to the material grown by MBE. It is assumed that these neutral defects are the Te nanocomplexes. Under ion milling, they are activated by mercury interstitials and form the donor centers with the concentration of 10 cm, which makes it possible to detect such defects by measurements of electrical parameters of the material. Under doping of HgCdTe with arsenic using high temperature cracking, the As dimers are present in the arsenic flow and block the neutral Te nanocomplexes to form donor AsTe complexes. The results of electrical studies are compared with the results of studies carried out by micro-Raman spectroscopy. [ABSTRACT FROM AUTHOR]

The anisotropic characteristics of an iron silicide (FeSi) epitaxial thin magnetic film grown on a Si(111) silicon vicinal surface with a misorientation angle of 0.14° have been measured by the ferromagnetic resonance method. It has been shown that the polar and azimuth misorientation angles of the crystallographic plane of the substrate can be determined simultaneously from the angular dependences of the ferromagnetic resonance field of the epitaxial film. The effective saturation magnetization of the film M = 1105 G and the constant of the cubic magnetocrystalline anisotropy K = 1.15 × 10 erg/cm have been determined. The misorientation of the substrate plane leads to the formation of steps on the film surface and, as a result, to the appearance of uniaxial magnetic anisotropy of the magnetic dipole nature with the constant K = 796 erg/cm. Small unidirectional magnetic anisotropy ( K = 163 erg/cm), which may be associated with symmetry breaking on the steps of the film and is due to the Dzyaloshinskii-Moriya interaction, has been detected. [ABSTRACT FROM AUTHOR]

Silicon vertically double diffused metal oxide semiconductor field effect transistor (VDMOSFET) shows a great promise for low and medium power applications and is economical when compared to their compound semiconductor counterparts. A silicon power MOSFET can be optimized using a newly proposed drift layer design strategy to increase the breakdown performance. The main difference between existing standard design and the proposed design is that, the new design uses two drift layers instead of a single drift layer with a similar process complexity. Silicon VDMOSFETs are designed and optimized through process and device simulations. The performance advantages like breakdown voltage and on current have been estimated through a combination of device and process simulations. The proposed design resulted in a significant increase in breakdown voltage from 25 to 95 V. The improvement in the breakdown voltage is attributed to reduction in the intrinsic electric field due to dopant atom re-distribution. Complete process sequence for realization of the proposed design is described. Overall system advantages gained from the implementation of newly proposed structure and process sequence in Si power devices have also been demonstrated through simulations. [ABSTRACT FROM AUTHOR]

Progress in nanotechnology requires new approaches to materials synthesis that make it possible to control material functionality down to the smallest scales. An objective of materials research is to achieve enhanced control over the physical properties of materials such as ferromagnets, ferroelectrics and superconductors. In this context, complex oxides and inorganic perovskites are attractive because slight adjustments of their atomic structures can produce large physical responses and result in multiple functionalities. In addition, these materials often contain ferroelastic domains. The intrinsic symmetry breaking that takes place at the domain walls can induce properties absent from the domains themselves, such as magnetic or ferroelectric order and other functionalities, as well as coupling between them. Moreover, large domain wall densities create intense strain gradients, which can also affect the material's properties. Here we show that, owing to large local stresses, domain walls can promote the formation of unusual phases. In this sense, the domain walls can function as nanoscale chemical reactors. We synthesize a two-dimensional ferromagnetic phase at the domain walls of the orthorhombic perovskite terbium manganite (TbMnO3), which was grown in thin layers under epitaxial strain on strontium titanate (SrTiO3) substrates. This phase is yet to be created by standard chemical routes. The density of the two-dimensional sheets can be tuned by changing the film thickness or the substrate lattice parameter (that is, the epitaxial strain), and the distance between sheets can be made as small as 5 nanometres in ultrathin films, such that the new phase at domain walls represents up to 25 per cent of the film volume. The general concept of using domain walls of epitaxial oxides to promote the formation of unusual phases may be applicable to other materials systems, thus giving access to new classes of nanoscale materials for applications in nanoelectronics and spintronics. [ABSTRACT FROM AUTHOR]

In this work heteroepitaxial stabilization with nanoscale control of the magnetic Co2FeO4 phase at 250 °C is reported. Ultrasmooth and pure Co2FeO4 thin films (5-25 nm) with no phase segregation are obtained on perovskite SrTiO3 single crystal (100) and (110) oriented substrates by atomic layer deposition (ALD). High resolution structural and chemical analyses confirm the formation of the Co-rich spinel metastable phase. The magneto-crystalline anisotropy of the Co2FeO4 phase is not modified by stress anisotropy because the films are fully relaxed. Additionally, high coervice fields, 15 kOe, and high saturation of magnetization, 3.3 μB per formula unit (at 10 K), are preserved down to 10 nm. Therefore, the properties of the ALD-Co2FeO4 films offer many possibilities for future applications in sensors, actuators, microelectronics, and spintronics. In addition, these results are promising for the use of ALD compared to the existing thin-film deposition techniques to stabilize epitaxial multicomponent materials with nanoscale control on a wide variety of substrates for which the processing temperature is a major drawback. [ABSTRACT FROM AUTHOR]

Ultra-thin films of the electron doped manganite La0.8Ce0.2MnO3 were grown in a layer-by-layer growth mode on SrTiO3 (001) substrates by pulsed laser interval deposition. High structural quality and surface morphology were confirmed by a combination of synchrotron based x-ray diffraction and atomic force microscopy. Resonant X-ray absorption spectroscopy measurements confirm the presence of Ce4þ and Mn2þ ions. In addition, the electron doping signature was corroborated by Hall effect measurements. All grown films show a ferromagnetic ground state as revealed by both dc magnetization and x-ray magnetic circular dichroism measurements and remain insulating contrary to earlier reports of a metal-insulator transition. Our results hint at the possibility of electron-hole asymmetry in the colossal magnetoresistive manganite phase diagram akin to the high-Tc cuprates. [ABSTRACT FROM AUTHOR]

Co2(1+x)Mn1-xSi1-x (x = 0.0-0.4) films are prepared to investigate the dependence of Gilbert damping constant on Co concentration. The evolution of structure and magnetic properties is also studied to analyse the influencing factors of damping constant. Due to the perfect film quality and good B2 ordering, the Co2MnSi (x = 0.0) film shows a small damping constant (α = 0.0054) and large saturation magnetization (Ms = 864 emu cm-3). The formation of Co antisites induces an increase in coercivity and damping constant. The abrupt jump of damping constant in the Co2.6Mn0.7Si0.7(x = 0.3) films is attributed to the disappearance of half-metallicity. [ABSTRACT FROM AUTHOR]

High-angle neutron diffraction was used to directly reveal the atomic-scale magnetic structure of a single-crystalline BiMn0.5Fe0.5O3 thin film deposited on a SrTiO3 (001) substrate. The BiMn0.5Fe0.5O3 phase exhibits distinctive magnetic properties that differentiate it from both parent compounds: BiFeO3 and BiMnO3. A transition to long-range G-type antiferromagnetism was observed below 120 K with a () propagation vector. A weak ferromagnetic behavior was measured at low temperature by superconducting quantum interference device (SQUID) magnetometry. There is no indication of the spin cycloid, known for BiFeO3, in the BiMn0.5Fe0.5O3 thin film. The neutron diffraction suggests a random distribution of Mn and Fe over perovskite B sites. [ABSTRACT FROM AUTHOR]

We report the experimental results of Fe and Fe3O4 nanostructures on GaAs(100) surfaces and hybrid Ferromagnetic/Semiconductor/Ferromagnetic (FM/SC/FM) spintronic devices. Element specific x-ray magnetic circular dichroism (XMCD) measurements have shown directly that Fe atoms on the GaAs(100)-4times6 surface are ferromagnetic. Within coverages of 2.5 to 4.8 ML superparamagnetic nanoclusters are formed and exhibiting strong uniaxial anisotropy, of the order of 6.0times105 erg/cm3. The coercivities of epitaxial Fe dot arrays films grown on GaAs(100) were observed to be dependent on the separation and size of the dots indicating that interdot dipolar coupling affects the magnetization processes in these dots. In addition Fe3O4 films grown on deformed GaAs(100) substrates have been observed to form nanostripes following the topography of the substrate and magneto-optical Kerr effect (MOKE) measurements showed that these nanostripes have uniaxial magnetic anisotropy with easy axis perpendicular to the length of the nanostripes. Meanwhile the FM/SC/FM vertical device has exhibited a biasing current dependent on MR characteristics, with a maximum change of 12% in the MR observed, indicating for the first time a large room temperature spin injection and detection [ABSTRACT FROM PUBLISHER]

Magnetic quantum-well (QW) states are probed with angle- and spin-resolved photoemission to address critical issues pertaining to the origin of the giant magnetoresistance (GMR) optimization and oscillatory coupling of magnetic multilayers. Two epitaxial systems are highlighted: Cu/Co(wedge)/Cu(100) and Cr/Fe(100)-whisker. The confinement of Cu sp-QW states by a Co barrier requires a characteristic Co thickness of 2.2/spl plusmn/0.6 /spl Aring/, which is consistent with the interfacial Co thickness reported to optimize the GMR of Permalloy-Cu structures. The controversial k-space origin of the 18-/spl Aring/ long period oscillation in Fe/Cr multilayers is identified by the vector that spans the d-derived "lens" feature of the Cr Fermi surface , based on the emergence of QW states with 17/spl plusmn/2 /spl Aring/ periodicity in this region. [ABSTRACT FROM PUBLISHER]

A GaN epilayer was grown on Al2O3 substrate by metal-organic chemical vapor deposition, and Co- ions with a dose of 3×1016 cm-2 were implanted into GaN at 350°C. The implanted samples were postannealed at 700°C-900°C to recrystallize the samples and to remove implantation damage. We have investigated the magnetic and structural properties of Co ion-implanted GaN by using X-ray diffraction (XRD), superconducting quantum interference device (SQUID) magnetometer, and X-ray photoelectron spectroscopy (XPS). XRD results did not show any peaks associated with the second phase formation, and only the diffraction from the GaN layer and substrate structure were observed. The temperature dependence of magnetization taken in zero-field-cooling and field-cooling conditions showed the features of superparamagnetic system in films annealed at 700°C-900°C. The magnetization curves at 5 K for samples annealed at 700°C-900°C exhibits ferromagnetic hysteresis loops, and the highest residual magnetization (MR) and coercivity (Hc) of MR=1.5×10-4 emu/g and Hc=107 Oe were found in the 800°C annealed sample. XPS measurement showed the metallic Co 2p core levels and the metallic valence band spectra for as-implanted and 700°C-900°C annealed samples. From these, it could be explained that the magnetic property of our films originated from Co and CoGa magnetic clusters. [ABSTRACT FROM PUBLISHER]

BaFeO3 (BFO) epitaxial thin films on (001) SrTiO3 substrates have been successfully produced by pulsed laser beam deposition. The epitaxially grown BFO was found to have tetragonal crystal structure with some amount of oxygen deficiencies. The magnetic susceptibilities of the samples strongly depended on the (hkl) directions of BFO varied in accordance with the crystalline directions, i.e., χ(100) < χ(110) < χ(001). The magnetic spin structure of the epitaxially grown BFO was speculated to be conventional antiferromagnetic. The remanent magnetization of the samples was found to depend on the amount of oxygen delicilncies significantly. This implies that the 180° superexchange interaction of Fe4+ - O2- - Fe4+ may possibly produce some kinds of ferromagnetic ordering. [ABSTRACT FROM AUTHOR]

We propose a magnetooptic modulator based on a thin-film iron garnet material. The Landau-Lifshitz equation, which governs magnetization dynamics, is combined with a beam propagation method to evaluate the performance of the device in the multigigahertz range. Bandwidth considerations and temporal response are discussed [ABSTRACT FROM PUBLISHER]

The effects of substrate on the strains of epitaxial TbFe/sub 2/(111) films, and consequently on the magnetization orientation, have been studied. Thermal strain from differential thermal contraction between substrates and the TbFe/sub 2/ films is considered to be the dominant factor in determining the film strain. Therefore, Al/sub 2/O/sub 3/(112~0), MgO(111), and CaF/sub 2/(111) substrates with an epitaxial W(110) buffer layer have been used to grow the TbFe/sub 2/ films. The magnetisation of the TbFe/sub 2/ films on the Al/sub 2/O/sub 3/ and MgO substrates with a tensile thermal strain is in the film plane, but that on the CaF/sub 2/ substrate with a compressive thermal strain is in the out-of-plane direction. An unknown soft magnetic material has been found at the interfacial region of the TbFe/sub 2/ film and the W buffer layer. [ABSTRACT FROM PUBLISHER]

Correlation between the thickness of the nonmagnetic layer and the magnetic anisotropy of epitaxial Co(11~00)/Cr(211)/MgO(110) bilayers was studied experimentally and analyzed theoretically. The Co thickness was held constant at 200 /spl Aring/ while the thickness of the Cr layer was varied between 6 and 100 /spl Aring/. Coercivity was found to decrease with increasing thickness of a continuous Cr layer: at low temperatures the observed data are in good agreement with a model of roughness induced magnetostatic anisotropy energy. [ABSTRACT FROM PUBLISHER]

Magnetoelastic effects due to internal stress strongly influence the magnetic properties of thin ferromagnetic films. Here we propose a method to create a tensile stress state, isotropic along the plane of the film, which superimposes on the intrinsic stress (also normally isotropic). Thus the study of the effects of deposition or epitaxial stresses onto anisotropy properties of thin films becomes feasible. As an application, magneto-optical polar Kerr hysteresis loop measurements have been carried out on Ni films electroplated on elastic bronze substrates; the magnetoelastic anisotropy created reduces the total in-plane anisotropy field of about 20% for a radial deformation of 3/spl middot/10/sup -3/, around 100 times the saturation magnetostriction of bulk Ni. [ABSTRACT FROM PUBLISHER]

Co/Mo bilayered films have been successfully grown on MgO(100) and MgO(110) substrates by molecular beam epitaxy. According to the reflection high energy electron diffraction and X-ray diffraction measurements the crystal structure of the film depends on the orientation of the buffer and substrate. The growth of biaxial Co(112~0)/Mo(100) on MgO(100) and of uniaxial Co(11~00)/Mo(211) on MgO(110) substrates has been confirmed. The anisotropic magnetoresistance (AMR) is strongly influenced by the Co orientation which is altered by growth on Mo/MgO(100) and MgO(110). In Co(112~0)/Mo(100) on MgO(110) AMR is isotropic for all in-plane fields. However, for Co(11~00)/Mo(211) on MgO(110) we observed enhancement of AMR along the easy axis at 10 K. [ABSTRACT FROM PUBLISHER]

We have observed giant magnetoresistance in spin valves using the PtMnSb Heusler alloy as either one or both of the two ferromagnetic component layers. Up to 0.5% MR has been measured in the CIP geometry in films consisting of (111) epitaxial PtMnSb grown on Al/sub 2/O/sub 3/ with Cu as a non-magnetic spacer and Co as the remaining ferromagnetic component. Attempts to pin the upper Co layer with the high coercivity ferromagnet Co/sub 80/Pt/sub 20/ helped decouple the magnetic layers but led to increased current shunting lowering the overall MR. We have also grown PtMnSb(111)/CuMnSb(111)/PtMnSb(111)/MnFe spin valves. Such spin valves showed a maximum GMR of 0.05%. We attribute this low value of MR to insufficient decoupling of the PtMnSb layers and possible interlayer mixing between the different Heusler alloys. [ABSTRACT FROM PUBLISHER]

Elastic and magnetic properties of ultrathin iron films on tungsten (110) are investigated. In situ film stress measurements during growth show stress values of 25 GPa per deposited monolayer. Our experiments indicate that the tremendous film stress triggers the formation of a misfit dislocation network at a coverage of 1.5 monolayers. The effect of the film stress and its spatial variation on the magnetic behavior are discussed. We find a high coercivity of order 0.3 T for 1.5 monolayer thick films. A model is presented that explains the high coercivity in terms of strong domain wall pinning. [ABSTRACT FROM PUBLISHER]

Thin films of Nd/sub 2/Fe/sub 14/B (/spl sim/30-60 nm) were grown with c-axis texture by means of molecular beam epitaxy. A two-phase structure is observed in both the X-ray diffraction and the hysteresis loops, due to an interfacial reaction during the initial growth. Coercivities are 1-2 T at 20 K, and the anisotropy fields are bulk-like. Microstructural analysis by atomic and magnetic force microscopies reveal lateral grain sizes of /spl sim/200 nm, which could explain the hard magnetic properties. [ABSTRACT FROM PUBLISHER]

Rare-earth-transition-metal thin films are successfully grown by magnetron sputtering onto single-crystal MgO substrates with epitaxial W buffer layers. The use of epitaxial W buffer layers allows oriented single-phase films to be grown. Sm-Co films grown onto W(100), have strong in-plane anisotropy and coercivities exceeding 5 T at 5 K whereas Fe-Sm films have strong perpendicular anisotropy and are magnetically soft. [ABSTRACT FROM PUBLISHER]