Control of the Oscillatory Interlayer Exchange Interaction with Terahertz Radiation

Beating pattern in radiation-induced oscillatory magnetoresistance in 2DES: coupling of plasmon-like and acoustic phonon modes

We present a microscopic theory on the observation of a beating pattern in the radiation-induced magnetoresistance oscillations at very low magnetic field. We con- sider that such a beating pattern develops as a result of the coupling between two oscillatory components: the first is a system of electron Landau states being harmon- ically driven by radiation. The second is a lattice oscillation, i.e., an acoustic phonon mode. We analyze the dependence of the beating pattern on temperature, radiation frequency and power. We conclude that the beating pattern is an evidence of the radiation-driven…

Highly efficient spin orbit torque in Pt/Co/Ir multilayers with antiferromagnetic interlayer exchange coupling

We have studied the spin orbit torque (SOT) in Pt/Co/Ir multilayers with 3 repeats of the unit structure. As the system exhibits oscillatory interlayer exchange coupling (IEC) with varying Ir layer thickness, we compare the SOT of films when the Co layers are coupled ferromagnetically and antiferromagnetically. SOT is evaluated using current induced shift of the anomalous Hall resistance hysteresis loops. A relatively thick Pt layer, serving as a seed layer to the multilayer, is used to generate spin current via the spin Hall effect. In the absence of antiferromagnetic coupling, the SOT is con…

Oscillatory Exchange Bias Controlled by RKKY in Magnetic Multilayers

Ferromagnetic/antiferromagnetic bilayers are interfaced with normal metal/ferromagnetic bilayers to form F*/AF/N/F valves. The N-spacer thickness is chosen such that it mediates strong indirect exchange (RKKY) between the outer magnetic layers, which varies in strength/direction depending on the N thickness and in direction on switching F. The system exhibits a strong modulation of the F*/AF exchange bias, oscillating in strength syncronously with the oscillation in the interlayer RKKY exchange across the normal metal spacer. The effect is explained as due to a superposition taking place withi…

Landauer-Büttiker方法在闭合弹道多层膜层间交换耦合计算中的应用

Application of the Landauer-Büttiker method to the calculation of interlayer exchange coupling in closed ballistic multi-layers

本文利用Landauer-Büttiker方法研究弹道多层膜从开放到闭合转变过程中自旋流行为，证明面外自旋流在闭合极限下给出与能量差定义完全一致的层间交换耦合表达式。

Persistent charge and spin currents in a 1D ring with Rashba and Dresselhaus spin-orbit interactions by excitation with a terahertz pulse

Persistent, oscillatory charge and spin currents are shown to be driven by a two-component terahertz laser pulse in a one-dimensional mesoscopic ring with Rashba-Dresselhaus spin orbit interactions (SOI) linear in the electron momentum. The characteristic interference effects result from the opposite precession directions imposed on the electron spin by the two SOI couplings. The time dependence of the currents is obtained by solving numerically the equation of motion for the density operator, which is later employed in calculating statistical averages of quantum operators on few electron eige…

Electric-Field Control of the Interlayer Exchange Coupling for Magnetization Switching

We propose an electric-field-controlled mechanism for magnetization switching assisted solely by the interlayer-exchange coupling (IEC) between the fixed and the free magnets, which are separated by two oxide barriers sandwiching a spacer material known for exhibiting large IEC. The basic idea relies on the formation of a quantum-well (QW) within the spacer material and controlling the transmission coefficient across the structure with an electric-field via the resonant tunneling phenomena. Using non-equilibrium Green's function (NEGF) method, we show that the structure can exhibit a bias-depe…

Sign-alternating photoconductivity and magnetoresistance oscillations induced by terahertz radiation in HgTe quantum wells

We report on the observation of terahertz radiation induced photoconductivity and of terahertz analog of the microwave-induced resistance oscillations (MIRO) in HgTe-based quantum well (QW) structures of different width. The MIRO-like effect has been detected in QWs of 20 nm thickness with inverted band structure and a rather low mobility of about 3 $\times$ 10$^5$ cm$^2$/V s. In a number of other structures with QW widths ranging from 5 to 20 nm and lower mobility we observed an unconventional non-oscillatory photoconductivity signal which changes its sign upon magnetic field increase. This e…

RKKY interaction in bilayer graphene

We study the RKKY interaction between two magnetic impurities located on same layer (intralayer case) or on different layers (interlayer case) in undoped bilayer graphene in the four-bands model, by directly calculating the Green functions in the eigenvalues and eigenvectors representation. Our results show that both intra- and interlayer RKKY interactions between two magnetic impurities located on same (opposite) sublattice are always ferromagnetic (antiferromagnetic). Furthermore we find unusual long-distance decay of the RKKY interaction in BLG. The intralyer RKKY interactions between two m…

通过含时密度泛函理论解读自旋电子学太赫兹发射器中自旋电流的起源及其对电磁辐射的印记

Deciphering the origin of spin current in spintronic terahertz emitters and its imprint on their electromagnetic radiation via time-dependent density functional theory

本研究采用含时密度泛函理论加Jefimenko方程方法，揭示了飞秒激光驱动Co/NM体系中太赫兹发射的自旋电流源于退磁化动力学量子泵浦，并阐明了电荷电流在不同时间范围对THz发射的主导作用及W层的特殊抑制机制。