Alternating current driven instability in magnetic junctions

Current driven spin-wave instability triggered by the anomalous Hall effect

We studied the effect of strong electric current on spin waves interacting relativistically with the current. The spin-wave spectrum is calculated at arbitrary direction of the wave vector. It is shown that the alternating Hall current generated by the alternating magnetic moment of the spin waves, reduces the spin-wave damping. At strong enough unpolarized dc current the damping changes sign, and the spin-wave amplitude starts to increase exponentially fast with time. The critical current for the spin-wave instability is determined mainly by the anomalous Hall effect, and can be much smaller …

交替偏置辅助退火非晶氧化物隧道结

Alternating Bias Assisted Annealing of Amorphous Oxide Tunnel Junctions

本研究提出交替偏置辅助退火技术，可调控非晶氧化铝隧道结的电学特性，提升电阻并降低损耗与缺陷，适用于多种电子器件。

Current effect on magnetization oscillations in a ferromagnet - antiferromagnet junction

Spin-polarized current effect is studied on the static and dynamic magnetization of the antiferromagnet in a ferromagnet - antiferromagnet junction. The macrospin approximation is generalized to antiferromagnets. Canted antiferromagnetic configuration and resulting magnetic moment are induced by an external magnetic field. The resonance frequency and damping are calculated, as well as the threshold current density corresponding to instability appearance. A possibility is shown of generating low-damping magnetization oscillations in terahertz range. The fluctuation effect is discussed on the ca…

Current induced spin injection and surface torque in ferromagnetic metallic junctions

Joint influence of two effects, namely, nonequilibrium spin injection by current, and current induced surface torque, on spin-valve type ferromagnetic metallic junctions is considered theoretically. The CPP configuration is assumed. The consideration is based on solving a coupled set of equations of motion for the mobile electron and lattice magnetizations. Boundary conditions are derived from the total magnetization flux continuity condition. A dispersion relation is derived for current dependent spin-wave fluctuations. The fluctuations become unstable under current density exceeding some thr…

Surface spin-transfer torque and spin-injection effective field in ferromagnetic junctions: Unified theory

We consider theoretically a current flowing perpendicular to interfaces of a spin-valve type ferromagnetic metallic junction. For the first time an effective approach is investigated to calculate a simultaneous action of the two current effects, namely, the nonequilibrium longitudinal spin injection and the transversal spin-transfer surface torque. Dispersion relation for fluctuations is derived and solved. Nonlinear problem is solved about steady state arising due to instability for a thick enough free layer.

Spintronics of metal ferromagnetic structures: New approaches in the theory and experiments

Two channels of the sd exchange interaction are considered in magnetic junctions. The first channel describes the interaction of transversal spins with the lattice magnetization. The second one describes the interaction of longitudinal spins with magnetization. We show the longitudinal channel leads to a number of significant effects: 1) drastic lowering of the current instability threshold down to three (or even more) orders of magnitude; 2) creation of large enough distortion of equilibrium due to current driven spin injection leading to inversion of energy spin subband populations and laser…

Phenomenological theory of current driven exchange switching in ferromagnetic nanojunctions

Phenomenological approach is developed in the theory of spin-valve type ferromagnetic junctions to describe exchange switching by current flowing perpendicular to interfaces. Forward and backward current switching effects are described and they may be principally different in nature. Mobile electron spins are considered as being free in all the contacting ferromagnetic layers. Joint action of the following two current effects is investigated: the nonequilibrium longitudinal spin-injection effective field and the transverse spin-transfer surface torque. Dispersion relation for fluctuations is d…

由交替多环烃区域与双碳链构成的一维杂化纳米对象的磁学与电子性质

Magnetic and electronic properties of 1D hybrid nanoobjects composed of alternating polycyclic hydrocarbon regions and double carbon chains

本研究基于密度泛函理论计算，揭示了由交替多环烃区域与双碳链构成的一维杂化纳米对象的磁学和电子性质可通过结构调控改变，明确了杂化泛函的重要性，为自旋电子学应用提供了新思路。

利用交变偏置辅助退火实现可调谐transmon量子比特的精密频率调谐

Precision frequency tuning of tunable transmon qubits using alternating-bias assisted annealing

本研究利用交变偏置辅助退火技术，在室温下实现可调谐transmon量子比特的精密频率调谐，验证了其对相干性的提升作用，展示了高保真门操作，为超导量子处理器规模化发展开辟新路径。

应变诱导的非交替补偿磁体及其在磁性隧道结器件设计中的应用

Strain-Induced Non-alter Compensated Magnet and Its Application to Magnetic Tunnel Junction Device Design

提出剪切应变策略将d波交替磁体调控为非交替补偿磁体，设计了RuO2/TiO2/RuO2磁性隧道结，显著提升了自旋劈裂与简并路径的TMR，为磁性器件设计提供新平台。

Stress-driven instability in growing multilayer films

We investigate the stress-driven morphological instability of epitaxially growing multilayer films, which are coherent and dislocation-free. We construct a direct elastic analysis, from which we determine the elastic state of the system recursively in terms of that of the old states of the buried layers. In turn, we use the result for the elastic state to derive the morphological evolution equation of surface profile to first order of perturbations, with the solution explicitly expressed by the growth conditions and material parameters of all the deposited layers. We apply these results to two…

Optical Properties of Layered Superconductors near the Josephson Plasma Resonance

We study the optical properties of crystals with spatial dispersion and show that the usual Fresnel approach becomes invalid near frequencies where the group velocity of the wave packets inside the crystal vanishes. Near these special frequencies the reflectivity depends on the atomic structure of the crystal provided that disorder and dissipation are very low. This is demonstrated explicitly by a detailed study of layered superconductors with identical or two different alternating junctions in the frequency range near the Josephson plasma resonance. Accounting for both inductive and charge co…