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The effect of potential barriers on the magnetoresistance of magnetic multilayered structures was investigated. The results showed that potentials generally affected the current in the plane of layers magnetoresistance. However, this behavior was not observed in the case of uniform scattering. In contrast, the potentials affected the current perpendicular to the plane of layers under all conditions.

In a semiconductor heterostructure, the Coulomb interaction is responsible for the electric current drag between two 2D electron gases across an electron impenetrable insulator. For two metallic layers separated by a ferromagnetic insulator (FI) layer, the electric current drag can be mediated by a nonequilibrium magnon current of the FI. We determine the drag current by using the semiclassical Boltzmann approach with proper boundary conditions of electrons and magnons at the metal-FI interface. [ABSTRACT FROM AUTHOR]

For transition-metal based ferromagnets, magnetic and spin transport properties are intimately correlated. By using an exchange interaction between conduction electrons and nonuniform magnetization vectors, we show that many spin-dependent phenomena in the nonequilibrium conditions can be understood in a unified picture. In particular, we discuss the generation of nonequilibrium spin density and spin current induced by domain wall motion. These induced spin density and spin currents produce an electromotive force, a domain wall resistance, inter-band electronic transitions between two spin channels, and an enhanced spatial-dependence of damping. As examples, we apply our formulations to study domain wall dynamics and corresponding induced charge currents or voltage. [ABSTRACT FROM AUTHOR]

Magnetization dynamics of magnetic alloys and multilayers at high temperatures are studied by solving the self-consistent Bloch equation. Upon a fast rise of the temperature, usually driven by a strong femtosecond laser pulse, the element-specific demagnetization shows rich dynamic characteristics. We find that the demagnetization time scales could differ substantially for each constitutes in the same alloy. We discuss plausible reasons for the experimental results of the laser induced magnetization switching of GdFe ferrimagnetic compounds. [ABSTRACT FROM AUTHOR]

The effect of multiple defects on the energy barrier of magnetization reversal in a one-dimensional magnetic nanowire is studied. By numerically solving the double Sine-Gordon equation via the finite-difference method, we obtain the energy saddle point through which the initial magnetic state jumps to the final ground states. The energy barrier which is defined as the difference between the energies of the saddle point and the initial states is calculated for various defect parameters. It is found that the energy barrier strongly depend on the number and distribution of the defects. For given defects, there exists an optimal distribution for a minimum energy barrier. [ABSTRACT FROM AUTHOR]

Spin Hall angle characterizes the rate of spin-charge current conversion and it has become one of the most important material parameters for spintronics physics and device application. A long-standing controversy is that the spin Hall angles for a given material measured by spin pumping and by spin Hall torque experiments are inconsistent and they could differ by as much as an order of magnitude. By using the linear response spin transport theory, we explicitly formulate the relation between the spin Hall angle and measured variables in different experiments. We find that the nonlocal conductivity inherited in the layered structure plays a key role to resolve conflicting values of the spin Hall angle. We provide a generalized scheme for extracting spin transport coefficients from experimental data. [ABSTRACT FROM AUTHOR]

By incorporating random interfacial exchange interaction into the Landau-Lifshitz-Gilbert equation, we show that magnetization reversal of exchange-biased films possesses unique hysteresis features. A detail magnetization reversal process for different ferromagnetic layer thickness is analyzed. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Aluminum nitride (AlN) ceramic is widely used in lots of fields, but its high-efficiency preparation still needs to be developed. In this paper, AlN nanoparticles are prepared from urea and aluminum chloride hydrate by a facile urea glass route in NH 3 atmosphere. The products are characterized by X-ray powder diffraction, laser particle size analyzer, scanning electron microscope and transmission electron microscope. The results show that the urea content present less effects on the crystal phase of the AlN ceramic powder. Hexagonal aluminum nitride (h -AlN) nanoparticles with high purity can be obtained when the heat treatment temperature is above 900 °C. The crystallite size of AlN nanoparticles is enlarged with increasing temperature. The optimized molar ratio of urea to aluminum salt is 6 and the sintering temperature is 1000 °C. The average crystallite size of this product is 17.0 nm and the average particle size (D 50) is 159.5 nm. The element distributions of N and Al in the AlN nanoparticles are highly coincident, which means that N and Al atoms in ceramic nanoparticles are well combined. • High purity AlN nanoparticles were prepared by a facile urea glass route in NH 3 atmosphere. • Pure h -AlN nanoparticles were obtained by increasing the temperature above 900 °C. • The microstructure of AlN nanoparticles were studied by HRTEM. [ABSTRACT FROM AUTHOR]

The article focuses on a self-consistent method for the spin-charge conversion for Pt and Pd with various ferromagnetic (FM) pumping sources including microwave photoresistance, inverse spin Hall effect measurements and effective spin-mixing conductance. It refers to an interfacial spin loss (ISL) in the spin current whose magnitude varies for different interfaces.

In magnetic materials, both electrons and magnons are capable of carrying angular momentum currents. An external electric field can efficiently drive a charge and spin current of electrons, but it is unable to directly produce a chargeless magnon current. The generation of the magnon current is conventionally achieved via thermal gradients or the electron spin injection from interfaces. Here, we investigate the magnon current induced by the momentum and angular momentum transfer from conduction electrons in magnetic layered systems. By using the generic exchange interaction between electrons and magnons, we derive the coupled diffusion equations for electron spins and magnons and we find (a) the ratio between the magnon current and the electric charge current is substantial at room temperature for conventional conducting ferromagnets, (b) the spin diffusion length of electrons is significantly modified by the presence of the nonequilibrium magnon density, and (c) the giant magnetoresistance of the magnetic multilayers for the current perpendicular to the plane of layers is reduced compared to the prior theory without taking into account the magnon current. [ABSTRACT FROM AUTHOR]

We report a large enhancement of thermally injected spin current in normal metal (NM)/antiferromagnet (AF)/yttrium iron garnet (YIG), where a thin AF insulating layer of NiO or CoO can enhance the spin current from YIG to a NM by up to a factor of 10. The spin current enhancement in NM/AF/YIG, with a pronounced maximum near the Néel temperature of the thin AF layer, has been found to scale linearly with the spin-mixing conductance at the NM/YIG interface for NM=3d, 4d, and 5d metals. Calculations of spin current enhancement and spin mixing conductance are qualitatively consistent with the experimental results. [ABSTRACT FROM AUTHOR]

In a bilayer consisting of an insulator and a ferromagnetic metal (FM), interfacial spin-orbit scattering leads to spin mixing of the two conducting channels of the FM, which results in an unconventional anisotropic magnetoresistance (AMR). We theoretically investigate the magnetotransport in such bilayer structures by solving the spinor Boltzmann transport equation with the generalized Fuchs-Sondheimer boundary condition that takes into account the effect of spin-orbit scattering at the interface. We find that the new AMR exhibits a peculiar angular dependence which can serve as a genuine experimental signature. We also determine the dependence of the AMR on film thickness as well as resistivity spin asymmetry of the FM. [ABSTRACT FROM AUTHOR]

Angular momentum transport in magnetic multilayered structures plays a central role in spintronic physics and devices. The angular momentum currents or spin currents are carried by either quasiparticles such as electrons and magnons, or by macroscopic order parameters such as local magnetization of ferromagnets. Based on the generic interface exchange interaction, we develop a microscopic theory that describes interfacial spin conductance for various interfaces among nonmagnetic metals, ferromagnetic insulators, and antiferromagnetic insulators. Spin conductance and its temperature dependence are obtained for different spin batteries including spin pumping, temperature gradient, and spin Hall effect. As an application of our theory, we calculate the spin current in a trilayer made of a ferromagnetic insulator, an antiferromagnetic insulator, and a nonmagnetic heavy metal. The calculated results on the temperature dependence of spin conductance quantitatively agree with the existing experiments. [ABSTRACT FROM AUTHOR]

Fieldlike spin-orbit torque in FeMn/Pt bilayers with ultrathin polycrystalline FeMn has been characterized through planar Hall effect measurements. A large effective field of 2.05?10-5 to 2.44?10-5Oe(A-1cm2) is obtained for FeMn in the thickness range of 2-5 nm. The experimental observations can be reasonably accounted for by using a macrospin model under the assumption that the FeMn layer is composed of two spin sublattices with unequal magnetizations. The large effective field corroborates the spin Hall origin of the effective field, considering the much smaller uncompensated net moments in FeMn as compared to NiFe. The effective absorption of spin current by FeMn is further confirmed by the fact that spin current generated by Pt in NiFe/FeMn/Pt trilayers can only travel through the FeMn layer with a thickness of 1-4 nm. By quantifying the fieldlike effective field induced in NiFe, a spin diffusion length of 2 nm is estimated in FeMn, consistent with values reported in the literature by ferromagnetic resonance and spin-pumping experiments. [ABSTRACT FROM AUTHOR]