Magnetic properties of epitaxial Fe3_3O4_4 films with various crystal orientations and TMR effect in room temperature

Fe$_3$O$_4$ is a ferrimagnetic spinel ferrite that exhibits electric conductivity at room temperature (RT). Although the material has been predicted to be a half metal according to ab-initio calculations, magnetic tunnel junctions (MTJs) with Fe$_3$O$_4$ electrodes have demonstrated a small tunnel magnetoresistance effect. Not even the sign of the TMR ratio has been experimentally established. Here, we report on the magnetic properties of epitaxial Fe$_3$O$_4$ films with various crystal orientations. The films exhibited apparent crystal orientation dependence on hysteresis curves. In particular, Fe$_3$O$_4$(110) films exhibited in-plane uniaxial magnetic anisotropy. With respect to the squareness of hysteresis, Fe$_3$O$_4$ (111) demonstrated the largest squareness. Furthermore, we fabricated MTJs with Fe$_3$O$_4$(110) electrodes, and obtained an TMR effect of -12\% at RT. The negative TMR ratio corresponded to the negative spin polarization of Fe$_3$O$_4$ predicted from band calculations

Spin-transfer switching and thermal stability in an FePt/Au/FePt nanopillar prepared by alternate monatomic layer deposition

We fabricated a current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) nanopillar with a 1-nm-thick FePt free layer having perpendicular anisotropy using the alternate monatomic layer deposition method. Nanopillars consisting of [Fe (1 monolayer (ML))/Pt (1 ML)]n (n: the number of the alternation period) ferromagnetic layers and an Au spacer layer showed spin-transfer induced switching at room temperature.Comment: 11 page

Electric Resistance of Magnetic Domain Wall in NiFe Wires with CoSm Pinning Pads (SOLID STATE CHEMISTRY-Artificial Lattice Allolys)

A NiFe wire of 1μm width with hard magnetic CoSm pinning pads and Cu electrodes was prepared by electron-beam lithography and lift-off technique. Using the exchange interaction between the NiFe wire and CoSm pads, magnetic structures with and without magentic domain walls were realizecd at zero external field. The electric resistance of the wall state was smaller than that of the no-wall state. The difference of the resistance can be explained by the anisotropic magnetoresistance effect in the domain walls

Electrostatic model of solid-state capacitor with ionizable charge traps

We present the analysis of a simple electrostatic model of a solid-state capacitor with ionizable charge traps. It shows a charge–voltage characteristic resembling a chemical battery. With a given withstanding voltage and the same geometry, the energy density of the capacitor with ionizable traps will be lower than that of an ordinary capacitor with metal electrodes

Magnetoresistance of Bloch-Wall-Type Magnetic Structures Induced in NiFe/CoSm Exchange-Spring Bilayers (SOLID STATE CHEMISTRY-Artificial Lattice Alloys)

The magnetoresistance (MR) originating from a magnetic structure with gradually rotating magnetic moments was studied using soft-magnetic (NiFe)/hard-magnetic (CoSm) bilayers. The main feature of the MR curves was explained as anisotropic magnetoresistance (AMR) effect. It was found that a giantmagnetoresistance-( GMR)-type effect coexisted, although the effect was very small in comparison with the AMR effect

Solvent Effects on the Transient Characteristics of Liquid-Gate Field Effect Transistors with Silicon Substrate

The transient characteristics of electric double layer (EDL) gated field-effect transistors with Si as an active semiconductor were studied using various electrolyte solutions of LiBF4 by applying a step-function voltage to determine the optimum electrolyte for semiconductor circuits using EDLs. The tR, determined by EDL dynamics in the present experiment, was minimum as a function of the kind of solvent used owing to the competing effects of the EDL thickness and viscosity. The responses of the electrolyte solutions with various solvents at the same concentration were classified into three categories on the basis of tR: slow response of a complex-forming solvent, intermediate response of protic solvents, and fast response of nonprotic solvents. The best response time was 55 µs when a 1.0 M acetonitrile solution was used as the liquid-gate insulator

Formation of graphite zigzag edges by cathodic electrochemical etching in acidic solution

We examined the edge structure of graphite formed by a cathodic electrochemical reaction in acid solutions associated with water electrolysis. Pole figures of the X-ray diffraction show that the edge orientation is parallel to the zigzag edge direction on a macroscopic scale. The polarization dependence of the G-band and D-band of the Raman spectra is consistent with the zigzag edge formation on a microscopic scale. It was found that the etched carbon atoms are converted to CH4 in the evolving gas and molecular species in the solution

Change in the Morphology of the Terrace Edges on Graphite Surfaces by Electrochemical Reduction

We found that graphite surfaces can be etched by electrochemical reduction in sulfuric acid. Terraces with straight edges crossing with 60o-multiple angles were found on surfaces by AFM observation. It suggests that crystallographic edges can be formed at room temperature in a controlled manner. Layer-by-layer etching of graphene sheets was possible by tuning the etching condition

Estimation of Gas Permeation Characteristics of Ultrahigh Barrier Edge Sealing Materials from Asymptotic Solution of Diffusion Equation

Materials and structures for water vapor barrier sealing are now actively studied, as the commercialization of organic electronic devices has become a reality. In this paper, we focus on the edge sealing barriers, in which diffusion plays an essential role. In the past, the diffusion-limited gas barrier properties were analyzed in the steady-state approximation, which is never reached within the device lifetime in the application for organic electronics. We analyze them using a simple analytical model. The diffusion before reaching the steady state is a strongly non-linear process, as is well known, and the length scale of approximately 1–10 mm is very important when a practical polymer resin is used for the edge seal

Carbon-Doped Hexagonal Boron Nitride: Analysis as π-Conjugate Molecules Embedded in Two Dimensional Insulator

We analyzed the electronic structures of carbon-doped hexagonal boron nitride, focusing on the comparison with the corresponding π-conjugate hydrocarbon molecules and odd-number substitution by first principle calculation. The band gaps are about the half that of the HOMO-LUMO gaps of corresponding hydrocarbons, except for the cis-butadiene structure in which aromatic hexagonal ring formation is important. Odd number doping makes metallic materials with very different work functions, depending upon the difference in B and N numbers, and has an expected application as electrodes for flexible devices