Tunnel Barrier Enhanced Voltage Signal Generated by Magnetization Precession of a Single Ferromagnetic Layer

Moriyama, Takahiro; Cao, Rong; Fan, Xin; Xuan, G.; Nikolić, Branislav K.; Tserkovnyak, Yaroslav; Kolodzey, J.; Xiao, John Q.

doi:10.1103/physrevlett.100.067602

Cited by 47 publications

(70 citation statements)

References 17 publications

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“…12,19 Here R AP is the resistance with antiparallel configuration of magnetizations in the F layers of thickness d F = 50, while R P is the junction resistance when magnetizations are parallel. Since both of these resistances are dominated by the tunnel barrier potential, they are computed for clean junctions.…”

Section: Extrinsic Soc In the Bulk Of F Layersmentioning

confidence: 99%

“…12,19 The thickness of the insulating barrier is d I = 5 atomic monolayers. The finite-size F|I|F or F|I|N multilayer is connected to macroscopic reservoirs via two semi-infinite ideal (i.e., disorder, spin and charge interaction-free) N leads to form a two-terminal device required for both NEGF and scattering theory analysis.…”

Section: Mtj Device Setup and Its Hamiltonianmentioning

confidence: 99%

“…The value of angle θ is controlled by the input microwave power (typically θ 20 • in the recent experiments 19 ). The operatorsĉ † iσ (ĉ iσ ) create (annihilate) electron with spin σ at site i = (i x , i y , i z ), and γ is the nearest neighbor hopping which sets the unit energy scale.…”

Section: Mtj Device Setup and Its Hamiltonianmentioning

confidence: 99%

“…On the other hand, surprisingly large voltage signal ∝ ω observed 19 in F|I|N semi-MTJs, which do not contain the second analyzing F layer, has remained unexplained in virtually all recent theories [16][17][18]20 of spin pumping in MTJs. Some of these theories 17,18 actually predict tiny voltage signal which being non-adiabatic ∝ ( ω) 2 is the second-order effect.…”

mentioning

confidence: 99%

“…In Sec. II we discuss how to tune parameters of the microscopic Hamiltonian in order to reproduce properties of MTJs and semi-MTJs employed in experiments, 12,19 such as their tunneling magnetoresistance, diffusive nature of transport within the F layers, finite spin-diffusion length in F layers and strong interfacial Rashba SOC. Section III discusses NEGF equations of motion and how to solve such equations after converting them into algebraic ones via double Fourier transform.…”

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confidence: 99%

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Charge pumping by magnetization dynamics in magnetic and semimagnetic tunnel junctions with interfacial Rashba or bulk extrinsic spin-orbit coupling

et al. 2012

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We develop a time-dependent nonequilibrium Green function (NEGF) approach to the problem of spin pumping by precessing magnetization in one of the ferromagnetic layers within F|I|F magnetic tunnel junctions (MTJs) or F|I|N semi-MTJs in the presence of intrinsic Rashba spin-orbit coupling (SOC) at the F|I interface or the extrinsic SOC in the bulk of F layers of finite thickness (F-ferromagnet; N-normal metal; I-insulating barrier). To express the time-averaged pumped charge current, or the corresponding dc voltage signal in an open circuit, we construct a novel solution to double-time-Fourier-transformed NEGF equations. The two energy arguments of NEGFs in this representation are connected by the Floquet theorem describing multiphoton emission and absorption processes. Within this fully quantum-mechanical treatment of the conduction electrons, we find that: (i) only in the presence of the interfacial Rashba SOC, the non-zero dc pumping voltage Vpump in F|I|N junctions can emerge at the adiabatic level (i.e., proportional to the microwave frequency), which could explain recent experiments on microwave-driven semi-MTJs [T. Moriyama et al., Phys. Rev. Lett. 100, 067602 (2008)]; (ii) a unique signature of this charge pumping phenomenon, where the Rashba SOC within the precessing F layer participates in the pumping process, is Vpump that changes sign as the function of the precession cone angle; (iii) unlike conventional spin pumping in MTJs in the absence of SOCs, where one emitted or absorbed microwave photon is sufficient to match the exact solution in the frame rotating with the magnetization, the presence of the Rashba SOC requires to take into account up to ten photons in order to reach the asymptotic value of pumped charge current; (iv) the disorder within F|I|F MTJs can enhance Vpump in the quasiballistic transport regime; (v) the extrinsic SOC in F|I|F MTJs causes spin relaxation and eventually the decay of Vpump which becomes negligible when the ratio of F layer thickness to the spin-diffusion length is around five. Our formalism can also be applied to electron and spin propagation in any noninteracting quantum system which is brought out of equilibrium by external fields of arbitrary strength or frequency.

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Section: Extrinsic Soc In the Bulk Of F Layersmentioning

confidence: 99%

Section: Mtj Device Setup and Its Hamiltonianmentioning

confidence: 99%

Section: Mtj Device Setup and Its Hamiltonianmentioning

confidence: 99%