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Spin diffusion theory is widely used to interpret experimental results in the field of spintronics. In this paper, we overview the detailed derivation of spin diffusion equation with emphasizing two main assumptions. We discuss po...
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Spin diffusion theory is widely used to interpret experimental results in the field of spintronics. In this paper, we overview the detailed derivation of spin diffusion equation with emphasizing two main assumptions. We discuss possible misinterpretations when applying the spin diffusion equation to spin-orbit torque experiment, where two assumptions of the spin diffusion theory are not applicable in general.
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We have investigated the spin pumping phenomenon in Fe80Co20/Ta bilayers of different thicknesses in which the ferromagnet grows epitaxially on MgO substrates. We have obtained a Gilbert damping constant for Fe80Co20 as low as alp...
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We have investigated the spin pumping phenomenon in Fe80Co20/Ta bilayers of different thicknesses in which the ferromagnet grows epitaxially on MgO substrates. We have obtained a Gilbert damping constant for Fe80Co20 as low as alpha = 1.3(1) x 10(-3), which is smaller than values generally reported in metallic ferromagnets. From the dependence of alpha with the Fe80Co20 thickness, we extracted the value of the effective spin mixing conductance g(up arrow down arrow) = 5.7(3) x 10(14) cm(-2). Analyzing the Ta and Fe80Co20 thickness dependence of the inverse spin Hall effect voltage, we obtained the transport parameters lambda(sd) = 1.1(3) nm and Theta(SH) = -0.024(3). We have developed an expression to quantify the efficiency of the spin pumping phenomenon in ferromagnetic/nonmagnetic metal bilayers. The calculated efficiency shows that the Fe80Co20/Ta system is up to an order of magnitude more efficient than other metallic ferromagnetic bilayers reported in the literature.
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We study theoretically the propagation and distribution of electron spin density in semiconductors within the drift-diffusion model in an external electric field. From the solution of the spin drift-diffusion equation, we derive t...
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We study theoretically the propagation and distribution of electron spin density in semiconductors within the drift-diffusion model in an external electric field. From the solution of the spin drift-diffusion equation, we derive the expressions for spin currents in the down-stream (DS) and up-stream (US) directions. We find that drift and diffusion currents contribute to the spin current and there is an electric field, called the drift-diffusion crossover field, where the drift and diffusion mechanisms contribute equally to the spin current in the DS direction, and that the spin current in the US direction vanishes when the electric field is very large. We calculate the drift-diffusion crossover field and show that the intrinsic spin diffusion length in a semiconductor can be determined directly from it if the temperature, electron density and both the temperature and electron density, respectively, are known for nondegenerate, highly degenerate and degenerate systems. The results will be useful in obtaining transport properties of the electron's spin in semiconductors, the essential information for spintronic technology.
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We present in this paper an analytic model to describe the effect of spin diffusion in CPP (current perpendicular to the plan) spin valves. Two ferromagnetic electrodes are separated by a nonmagnetic metal, organic or inorganic se...
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We present in this paper an analytic model to describe the effect of spin diffusion in CPP (current perpendicular to the plan) spin valves. Two ferromagnetic electrodes are separated by a nonmagnetic metal, organic or inorganic semiconducting spacer. We base our calculations on the evolution of the spin polarized density of states of the saturated ferromagnetic electrodes under an applied rotating magnetic field and the spin diffusion in the spacer. Without treating the mechanism of spin relaxation and dephasing in the spacer, we establish a general model with the cosine evolution of the magnetoresistance modulated by the effect of spin diffusion. Throughout our treatment we consider a tunnel junction at the interface between each ferromagnetic electrode and the spacer.
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This is a tutorial describing how the time-dependent diffusion coefficient D(t) of mobile molecules confined in pores or cells carries information about the confining geometry. At early times, D(t) = D_1[1 - (4/9 (pi)~(1/2)) (S/V_...
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This is a tutorial describing how the time-dependent diffusion coefficient D(t) of mobile molecules confined in pores or cells carries information about the confining geometry. At early times, D(t) = D_1[1 - (4/9 (pi)~(1/2)) (S/V_P)(D_0t)~(1/2)] gives, irrespective of details, the pore surface to volume ratio (S/V_P), which is a measure of microscopic length. Here D_0 is the bulk unrestricted diffusion coefficient. At long times, D(t) reaches a limiting value D_0/ alpha at a rate that depends on macroscopic length scales characteristic of the medium. The geometrical parameter "tortuosity" alpha plays an important role in various transport processes in porous media, such as the electrical conductivity. Extensions of these concepts to permeable pore walls, fluid identification by combining diffusion with relaxation, restricted diffusion in inhomogeneous magnetic fields leading to edge enhancement, and fractal surfaces are briefly described.
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We theoretically investigate a spin-mediated conversion from fluid dynamics to voltage, known as spin hydrodynamic generation (SHDG), in oscillatory and transient unsteady flows. We consider unsteady flows of liquid metal between ...
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We theoretically investigate a spin-mediated conversion from fluid dynamics to voltage, known as spin hydrodynamic generation (SHDG), in oscillatory and transient unsteady flows. We consider unsteady flows of liquid metal between two parallel infinite planes and then calculate its vorticity fields based on die Navier-Stokes equation for an incompressible viscous fluid. The spin accumulation and spin current generated by unsteady flows are derived using a spin-diffusion equation, including spin-vorticity coupling, which is a couple of angular momentum between electron spin and vorticity field in unsteady flows. The estimation of SHDG in liquid mercury flow suggests that an observable magnitude of voltage can be induced in unsteady flows. Our results are expected to enable the realization of high-speed spin devices with unsteady flows and broaden the range of fluid spintronics applicability.
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Spin diffusion and spin-lattice relaxation in solids containing paramagnetic impurities under influence of a multiple-pulse spin-locking radio-frequency sequence are studied theoretically and experimentally. The diffusion equation...
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Spin diffusion and spin-lattice relaxation in solids containing paramagnetic impurities under influence of a multiple-pulse spin-locking radio-frequency sequence are studied theoretically and experimentally. The diffusion equation obtained provides a clue for determination of the time dependent magnetization. The spin-lattice relaxation time is calculated as a function of the correlation time and multiple-pulse field parameters. From the experimental data the spin diffusion coefficient, the radius of the spin diffusion barrier, and the correlation time for very slow molecular motion in polycrystalline (C_2F)_n system are estimated and found to be D ～ 7.1 × 10~(-12) cm~2/s, r_c ～4.8 × 10~(-10) m, and τ_c ～ 10.2 μs, respectively.
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摘要 :
Spin diffusion and spin-lattice relaxation in solids containing paramagnetic impurities under influence of a multiple-pulse spin-locking radio-frequency sequence are studied theoretically and experimentally. The diffusion equation...
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Spin diffusion and spin-lattice relaxation in solids containing paramagnetic impurities under influence of a multiple-pulse spin-locking radio-frequency sequence are studied theoretically and experimentally. The diffusion equation obtained provides a clue for determination of the time dependent magnetization. The spin-lattice relaxation time is calculated as a function of the correlation time and multiple-pulse field parameters. From the experimental data the spin diffusion coefficient, the radius of the spin diffusion barrier, and the correlation time for very slow molecular motion in polycrystalline (C_2F)_n system are estimated and found to be D ～ 7.1 × 10~(-12) cm~2/s, r_c ～4.8 × 10~(-10) m, and τ_c ～ 10.2 μs, respectively.
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The theory of NQR spin diffusion is extended to the case of spin lattice relaxation and spin diffusion in an inhomogeneous field. Two coupled equations describing the mutual relaxation and the spin diffusion of the nuclear magneti...
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The theory of NQR spin diffusion is extended to the case of spin lattice relaxation and spin diffusion in an inhomogeneous field. Two coupled equations describing the mutual relaxation and the spin diffusion of the nuclear magnetization and dipolar energy were obtained by using the method of nonequilibrium state operator. The equations were solved for short and long times approximation corresponding to the direct and diffusion relaxation regimes.
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