Nanoscale Spin Injector Driven by a Microwave Voltage

Abstract

We propose an electrically driven spin injector into normal metals and semiconductors, which is based on a magnetic tunnel junction (MTJ) subjected to a microwave voltage. Efficient functioning of such an injector is provided by electrically induced magnetization precession in the "free" layer of MTJ, which generates the spin pumping into a metallic or semiconducting overlayer. We theoretically describe the spin and charge dynamics in the CoFeB/MgO/CoFeB/Au(GaAs) heterostructures. First, the magnedynamics in the free CoFeB layer is quantified with the account of a spin-transfer torque and a voltage-controlled magnetic anisotropy. By numerically solving the magnetodynamics equation, we determine dependences of the precession amplitude on the frequency $f$ and magnitude $V_{\max }$ of the ac voltage applied to the MTJ. It is found that the frequency dependence changes drastically above the threshold amplitude $V_{\max }\approx 200$mV, exhibiting a break at the resonance frequency $f_{\mathrm{res}}$ due to nonlinear effects. The results obtained for the magnetization dynamics are used to describe the spin injection and pumping into the Au and GaAs overlayers. Since the generated spin current creates additional charge current owing to the inverse spin Hall effect, we also calculate distribution of the electric potential in the thick Au overlayer. The calculations show that the arising transverse voltage becomes experimentally measurable at $f=f_{\mathrm{res}}$. Finally, we evaluate the spin accumulation in a long n${}^{+}$-GaAs bar coupled to the MTJ and determine its temporal variation and spatial distribution along the bar. It is found that the spin accumulation under resonant excitation is large enough for experimental detection even at micrometer distances from the MTJ. This result demonstrates high efficiency of the described nanoscale spin injector.

14 pages, 14 figures

References in corpus (27)

• Spintronics: Fundamentals and applications
• Microwave Oscillations of a Nanomagnet Driven by a Spin-Polarized Current
• Basic obstacle for electrical spin-injection from a ferromagnetic metal into a diffusive semiconductor
• Enhanced Gilbert Damping in Thin Ferromagnetic Films
• Nonlocal magnetization dynamics in ferromagnetic heterostructures
• Theory of electrical spin injection: Tunnel contacts as a solution of the conductivity mismatch problem
• Spin pumping and magnetization dynamics in metallic multilayers
• Electrical Detection of Spin Transport in Lateral Ferromagnet-Semiconductor Devices
• Quantifying spin Hall angles from spin pumping: Experiments and Theory
• Detection and quantification of inverse spin Hall effect from spin pumping in permalloy/normal metal bilayers
• Spin Injection and Detection in Magnetic Nanostructures
• Bias-driven large power microwave emission from MgO-based tunnel magnetoresistance devices
• Spin battery operated by ferromagnetic resonance
• Acoustically driven ferromagnetic resonance
• Dynamic exchange coupling in magnetic bilayers
• Spin-transfer-driven ferromagnetic resonance of individual nanomagnets
• Voltage-Induced Ferromagnetic Resonance in Magnetic Tunnel Junctions
• Spin pumping with coherent elastic waves
• First-principles study of magnetization relaxation enhancement and spin-transfer in thin magnetic films
• Giant spin-torque diode sensitivity at low input power in the absence of bias magnetic field
• Spin-Torque Driven Magnetization Dynamics: Micromagnetic Modelling
• Enhancement of the spin pumping efficiency by spin-wave mode selection
• Giant interfacial perpendicular magnetic anisotropy in MgO/CoFe/capping layer structures
• Spin diffusion length and polarization of ferromagnetic metals measured by spin-absorption technique in lateral spin valves
• Spin-torque driven ferromagnetic resonance in a nonlinear regime
• Magnetization dynamics and spin pumping induced by standing elastic waves
• Spin injection and pumping generated by a direct current flowing through a magnetic tunnel junction

Cited by in corpus (2)

• Anomalous Gilbert Damping and Duffing Features of the SFS {\boldmath ${\phi }_0$} Josephson Junction
• Energy-efficient spin injector into semiconductors driven by elastic waves