We show that in YIG-Pt bi-layers, which are widely used in experiments on the spin transfer torque and spin Hall effects, the spin-wave amplitude significantly decreases in comparison to a single YIG film due to the excitation of microwave eddy currents in a Pt coat. By introducing a novel excitation geometry, where the Pt layer faces the ground plane of a microstrip line structure, we suppressed the excitation of the eddy currents in the Pt layer and, thus, achieved a large increase in the transmission of the Damon-Eshbach surface spin wave. At the same time, no visible influence of an external dc current applied to the Pt layer on the spin-wave amplitude in the YIG-Pt bi-layer was observed in our experiments with YIG films of micrometer thickness.
While current-induced torque by orbital current has been experimentally found in various structures, evidence for its reciprocity has been missing so far. Here, we report experimental evidence of strong inverse orbital torque in YIG/Pt/CuOx (YIG = Y3Fe5O12) mediated by spin-orbital entangled electronic states in Pt. By injecting spin current from YIG to Pt by the spin pumping via ferromagnetic resonance and by the spin Seebeck effect, we find a pronounced inverse spin Hall effect-like signal. While a part of the signal is explained as due to the inverse spin-orbital Hall effect in Pt, we also …
Exchange magnetic field torques in YIG/Pt bilayers observed by the spin-Hall magnetoresistance
利用自旋霍尔磁阻（SMR）测量了钇铁石榴石薄膜对Pt薄膜自旋积累的有效场力矩。结果，可以电测量铁磁绝缘层的磁化方向。实验的横向和纵向电阻是很好地描述的SMR的理论模型的直接和逆自旋霍尔效应，对于不同的Pt厚度[3，4，8和35 nm]。采用Pt的自旋霍尔角$θ_{SH}=0.08$，得到了Pt的自旋扩散长度（$λ=1.1\pm0.3$ nm）以及自旋混合电导的实部（$G_r=(7\pm3)\times10^{14}Ω^{-1}$ m $^{-2}$）和虚部（$G_i=(5\pm3)\times10^{13}Ω^{-1}$ m $^{-2}$）及其比值（$G_r/G_i=16\pm4$）.
Study of the formation and evolution of large scale, ordered structures is an enduring theme in science. The generation, evolution and control of large sized magnetic domains are intriguing and challenging tasks, given the complex nature of competing interactions present in any magnetic system. Here, we demonstrate large scale non-coplanar ordering of spins, driven by picosecond, megagauss magnetic pulses derived from a high intensity, femtosecond laser. Our studies on a specially designed Yttrium Iron Garnet (YIG)/dielectric/metal film sandwich target, show the creation of complex, large, con…
Coherent spin pumping in a strongly coupled magnon-magnon hybrid system
我们在坡莫合金/钇铁石榴石（Py/YIG）双层膜的磁振子-磁振子混合模式中实验确定了相干自旋泵浦。利用宽带铁磁共振，观察到一个“避免交叉”之间的统一模式的Py和自旋波模式的YIG由于类场界面交换耦合。我们还确定了额外的线宽抑制和增强的同相和异相混合模式，分别为\textcolor{black}{which can be interpreted as concerted dampinglike torque from spin pumping}。我们的分析预测的反比例的fieldlike和dampinglike扭矩的平方根的Py厚度，这与实验定量一致。
Estimation of spin-orbit torques in the presence of current-induced magnon creation and annihilation
Université de Strasbourg, CNRS, Institut de Physique et Chimie des Matériaux de Strasbourg（斯特拉斯堡大学，法国国家科学研究中心，斯特拉斯堡材料与化学物理研究所）；ETH Zurich（苏黎世联邦理工学院）；Politecnico di Milano（米兰理工大学）
Finding efficient ways of manipulating magnetic bits is one of the core goals in spintronic research. Electrically-generated spin-orbit torques (SOTs) are good candidates for this and the search for materials capable of generating highly-efficient SOTs has gained a lot of traction in the recent years. While antiferromagnet/ferromagnet bilayer structures have been employed extensively for passive applications, e.g. by using exchange bias fields, their active properties are not yet widely employed. Here we show the presence of large interfacial SOTs in bilayer of a ferromagnet and the two-dimens…
Investigation of anomalous-Hall and spin-Hall effects of antiferromagnetic IrMn sandwiched by Pt and YIG layers
本文研究了Pt/Ir 20 Mn 80/Y3 Fe 5 O 12（Pt/IrMn/YIG）异质结的非线性霍尔电阻（AHR）、各向异性磁电阻（AMR）和磁化强度随温度和IrMn层厚度的变化关系。与Pt/YIG双层膜相比，AHR的幅度显著增强。在较高的温度下，增强更加深刻，并且在IrMn厚度为3 nm处达到峰值。在10-300 K的温度范围内观察到的自旋霍尔磁电阻（SMR）表明，在Pt层中产生的自旋电流可以穿透IrMn层的整个厚度与YIG层相互作用。传统的各向异性磁阻（CAMR）的缺乏意味着插入的IrMn层之间的Pt和YIG有效地抑制了磁邻近效应（MPE）上的感应Pt的时刻由YIG。我们的研究结果表明，在Pt/IrMn/YIG异质结构中的InMn插入的双重作用是阻止MPE和传输Pt和YIG层之间的自旋电流。我们讨论了增强AHR的可能机制。
We demonstrate the laser-induced control over spin-wave (SW) transport in the magnonic crystal (MC) waveguide formed from the semiconductor slab placed on the ferrite film. We considered bilayer MC with periodical grooves performed on the top of the n-type gallium arsenide slab side that oriented to the yttrium iron garnet film. To observe the appearance of magnonic gap induced by laser radiation, the fabricated structure was studied by the use of microwave spectroscopy and Brillouin light-scattering. We perform detailed numerical studies of this structure. We showed that the optical control o…
Spin transport is crucial for future spintronic devices operating at bandwidths up to the terahertz (THz) range. In F|N thin-film stacks made of a ferro/ferrimagnetic layer F and a normal-metal layer N, spin transport is mediated by (1) spin-polarized conduction electrons and/or (2) torque between electron spins. To identify a cross-over from (1) to (2), we study laser-driven spin currents in F|Pt stacks where F consists of model materials with different degrees of electrical conductivity. For the magnetic insulators YIG, GIG and maghemite, identical dynamics is observed. It arises from the TH…
Current-induced spin torques in layered magnetic heterostructures have many commonalities across broad classes of magnetic materials. These include not only collinear ferromagnets, ferrimagnets, and antiferromagnets, but also more complex noncollinear spin systems. We develop a general Lagrangian-Rayleigh approach for studying the role of dissipative torques, which can pump energy into long-wavelength magnetic dynamics, causing dynamic instabilities. While the Rayleigh structure of such torques is similar for different magnetic materials, their consequences depend sensitively on the nature of …
We study theoretically domain wall (DW) magnons-elementary collective excitations of magnetic DWs -- in easy-axis layered van der Waals (vdW) antiferromagnets, where they behave as normal modes of coupled spin superfluids. We uncover that, due to spin-charge coupling in vdW magnets, such DW magnons can be activated by voltage-induced torques, thereby providing a path for their low-dissipation and nanoscale excitation. Moreover, the electrical activation and the number of DW magnons at a frequency can be controlled by applying symmetry-breaking static magnetic field, adding tunability of signal…
Since the discovery of the spin orbit torque (SOT) induced by spin Hall effect in heavy metals, much effort has been devoted to understanding the mechanism of the charge-to-spin conversion as well as to developing new schemes for high speed, low energy magnetic recording technologies. While fast switching has been demonstrated in three terminal magnetic tunnel junctions (3T-MTJs) through applying short voltage pulses in the heavy metal channel, detailed understanding of the switching mechanism is lacking due to the complexity of the multi-layered magnetic structure and the three-terminal geome…
Engineering magnetic anisotropy in a ferro- or ferrimagnetic (FM) thin film is crucial in spintronic device. One way to modify the magnetic anisotropy is through the surface of the FM thin film. Here, we report the emergence of a perpendicular magnetic anisotropy (PMA) induced by interfacial interactions in a heterostructure comprised of a garnet ferrimagnet, Y3Fe5O12 (YIG), and the low-symmetry, high spin orbit coupling (SOC) transition metal dichalcogenide, WTe2. At the same time, we also observed an enhancement in Gilbert damping in the WTe2 covered YIG area. Both the magnitude of interface…
Magnetic fingerprint in a ferromagnetic wire: Spin torque diode effect and induction of the DC voltage spectrum inherent in the wire under application for RF current
Low crystal symmetry of magnetic van der Waals materials naturally promotes spin-orbital complexity unachievable in common magnetic materials used for spin-orbit torque switching. Here, using first-principles methods, we demonstrate that an interplay of spin and orbital degrees of freedom has a profound impact on spin-orbit torques in a prototype van der Waals ferromagnet: Fe$_3$GeTe$_2$ (FGT). While we show that bulk FGT hosts strong "hidden" current-induced torques harvested by each of its layers, we uncover that their origin alternates between the conventional spin flux torque and the so-ca…
Frustrated topological spin textures have unique properties that may enable novel spintronic applications, such as helicity-based information storage and computing. Here, we report the statics and current-induced dynamics of two-dimensional (2D) pancake skyrmions in a stack of weakly coupled frustrated magnetic monolayers, which form a three-dimensional (3D) skyrmion string. The Bloch-type skyrmion string is energetically more stable than its Néel-type counterpart. It can be driven into translational motion by the dampinglike spin-orbit torque and shows the damping-dependent skyrmion Hall effe…
First harmonic measurements of the spin Seebeck effect
我们目前的测量自旋塞贝克效应（SSE）的技术，结合交流（AC）和直流（DC）。该方法被应用到亚铁磁性绝缘体/重金属双层膜，Y $_3$ Fe $_5$ O $_{12}$（YIG）/Pt。通常，SSE测量使用AC电流来产生交变温度梯度，并以两倍AC频率测量由重金属中的逆自旋霍尔效应产生的电压。在这里，我们表明，当焦耳加热与AC和DC偏置电流，SSE响应发生在AC电流驱动的频率，可以大于二次谐波SSE响应。我们比较了第一和第二谐波响应，并表明它们是一致的SSE。电压响应的场依赖性被用来表征类阻尼和类场转矩。该方法可用于研究温度梯度引起的非线性热电效应和自旋动力学。
The interface between a ferro-/ferrimagnetic insulator and a normal metal can support spin currents polarized collinear with and perpendicular to the magnetization direction. The flow of angular momentum perpendicular to the magnetization direction ("transverse" spin current) takes place via spin torque and spin pumping. The flow of angular momentum collinear with the magnetization ("longitudinal" spin current) requires the excitation of magnons. In this article we extend the existing theory of longitudinal spin transport [Bender and Tserkovnyak, Phys. Rev. B 91, 140402(R) (2015)] in the zero-…
Spin-orbit torque (SOT) driven deterministic control of the magnetization state of a magnet with perpendicular magnetic anisotropy (PMA) is key to next generation spintronic applications including non-volatile, ultrafast, and energy efficient data storage devices. But, field-free deterministic switching of perpendicular magnetization remains a challenge because it requires an out-of-plane anti-damping torque, which is not allowed in conventional spin source materials such as heavy metals (HM) and topological insulators due to the system's symmetry. The exploitation of low-crystal symmetries in…
We investigated temperature dependent current driven spin-orbit torques in magnetron sputtered Ru2Sn3 (4 and 10 nm) /Co20Fe60B20 (5 nm) layered structures with in-plane magnetic anisotropy. The room temperature damping-like and field-like spin torque efficiencies of the amorphous Ru2Sn3 films were measured to be 0.14 +- 0.008 (0.07 +- 0.012) and -0.03 +- 0.006 (-0.20 +- 0.009), for the 4 (10 nm) films respectively, by utilizing the second harmonic Hall technique. The large field-like torque in the relatively thicker Ru2Sn3 (10 nm) thin film is unique compared to the traditional spin Hall mater…
Observation of Ultrafast Coherent and Incoherent Spin Torques via Terahertz Spin-Hall Magnetoresistance
Charles University（查理大学）；University of Konstanz（康斯坦茨大学）；Freie Universität Berlin（柏林自由大学）；Czech Academy of Sciences（捷克科学院）；Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy（马克斯·玻恩非线性光学和短脉冲光谱研究所）；Johannes Gutenberg-Universität Mainz（美因茨约翰内斯·古腾堡大学）；Fudan University（复旦大学）；Shanghai Research Center for Quantum Sciences（上海量子科学研究中心）；Martin-Luther-Universität, Halle（哈雷马丁·路德大学）
The discovery of an ever increasing family of atomic layered magnetic materials, together with the already established vast catalogue of strong spin-orbit coupling (SOC) and topological systems, calls for some guiding principles to tailor and optimize novel spin transport and optical properties at their interfaces. Here we focus on the latest developments in both fields that have brought them closer together and make them ripe for future fruitful synergy. After outlining fundamentals on van der Waals (vdW) magnetism and SOC effects, we discuss how their coexistence, manipulation and competitio…
The superposition of flexoelectronic doping and topological phonons give rise to topological electronic magnetism of phonon in an inhomogeneously strained Si in the bilayer structure with metal. In case of ferromagnetic metal and Si bilayer structure, the flexoelectronic doping will also give rise to larger spin current, which will lead to large spin to charge conversion due to topological electronic magnetism of phonon. By applying a temperature difference to ferromagnetic metal/Si bilayer structure under an applied strain gradient, a large thermoelectric response can be generated. In this ex…
Pushing down the lateral dimension of single and coupled magnetic dots to the nanometric scale: characteristics and evolution of the spin-wave eigenmodes
