We demonstrate a large enhancement of the spin accumulation in monolayer graphene following electron-beam induced deposition of an amorphous carbon layer at the ferromagnet-graphene interface. The enhancement is 10^4-fold when graphene is deposited onto poly(methyl metacrylate) (PMMA) and exposed with sufficient electron-beam dose to cross-link the PMMA, and 10^3-fold when graphene is deposited directly onto SiO2 and exposed with identical dose. We attribute the difference to a more efficient carbon deposition in the former case due to an increase in the presence of compounds containing carbon, which are released by the PMMA. The amorphous carbon interface can sustain very large current densities without degrading, which leads to very large spin accumulations exceeding 500 microeVs at room temperature.
Modulations of interfacial Dzyaloshinskii-Moriya interaction (iDMI) on current-driven dynamics of 180$^{\circ}$ domain walls (180DWs) in long and narrow spin valves (LNSVs) with heavy-metal caplayers are systematically investigated. We focus on LNSVs with in-plane magnetic anisotropy in their free layers. For planar-transverse polarizers (pinned layers of LNSVs), the Walker breakdown can be postponed considerably (practical infinity) by iDMI. More interestingly, the originally unstable traveling mode is also stabilized by iDMI with high saturation velocity thus serves as fast carrier of inform…
Detection of the interfacial exchange field at a ferromagnetic insulator-nonmagnetic metal interface with pure spin currents
在铁磁金属(NM)和铁磁绝缘体(FI)之间的界面处,自旋电流可以与磁化相互作用,导致自旋电流的调制。在这些FI-NM界面的界面交换场可以通过将该界面放置成与横向自旋阀(LSV)器件的自旋输运通道接触并观察额外的自旋弛豫过程来探测。研究了铁磁绝缘体EuS(EuS-LSV)和钇铁石榴石YPDMATHABMM Fe $_5$ O $_{12}$(YIG-LSV)附近的Cu自旋输运通道的横向自旋阀器件中的界面交换场.将自旋信号与在具有MgO或AlO $_x$覆盖的单晶硅/SiO $_2$衬底上制造的参考横向自旋阀器件进行比较。EuS-LSV和YIG-LSV中的非局域自旋阀信号分别低约4倍和6倍。自旋信号的抑制归因于由于界面自旋轨道场而在Cu-EuS(或Cu-YIG)界面处增强的表面自旋翻转概率。除了自旋信号的抑制外,我们还发现在$T \sim$ 30 K处的自旋信号中广泛观察到的低温峰在与EuS或YIG接触的情况下向更高的温度移动。不同注入器-检测器距离的自旋信号的温度依赖性揭示了在这些界面处的波动交换场导致额外的自旋退相干,其除了常规的自旋弛豫源之外还限制了自旋弛豫时间。结果表明,纯自旋电流随温度变化的测量方法可以用来探测铁磁绝缘体-铁磁金属界面的界面交换场。
Spin-valve effects in point contacts to exchange biased Co40Fe40B20 films
本文研究了反铁磁Mn_(80)Ir_(20)交换偏置的不同厚度的非晶铁磁体(F)Co_(40)Fe_(40)B_(20)薄膜与正常金属(N)点接触的非线性电流-电压特性和磁电阻。观察到这种F-N接触电导的表面自旋阀效应。交换偏置的影响被发现是成反比的Co 40 Fe 40 B 20膜的厚度。我们在单交换钉扎铁磁薄膜上观察到的这种行为以及其他磁输运效应与传统三层自旋阀中发现的性质相似。
We present and verify experimentally a universal theoretical framework for the description of spin-charge interconversion in non-magnetic metal/insulator structures with interfacial spin-orbit coupling (ISOC). Our formulation is based on drift-diffusion equations supplemented with generalized boundary conditions. The latter encode the effects of ISOC and relate the electronic transport in such systems to spin loss and spin-charge interconversion at the interface, which are parameterized, respectively, by $G_{\parallel/\perp}$ and $σ_{\rm{sc/cs}}$. We demonstrate that the conversion efficiency …
Nb/CuNi Sandwiches as Superconducting Spin-Valve Core Structures
我们已经研究了CuNi/Nb/CuNi三层,因为最近已经被用作自旋阀类器件的核心结构[J. Y. Gu等人,物理修订版信函89,267001(2002)]来研究CuNi层的磁结构对超导Nb的临界温度Tc的影响。在复制了几mK的Tc位移后,我们继续探索该结构的性能极限。结果表明,我们发现的Tc位移非常接近这种特殊材料系统的基本极限。超导体的厚度与相干长度之比和界面透明性是限制Tc漂移的主要因素。
Two-dimensional electron gas in a metal/amorphous oxide interface with spin orbit interaction
在金属/非晶界面中形成具有高迁移率的新型二维电子气(2DEG)激发了关于这些2DEG的形成和新特性的持续辩论。在这里,我们报告了一个光学研究,基于红外光谱椭圆偏振法,金属和非晶半导体氧化物(Cu/Bi $_2$ O $_3$)接口,确认形成的2DEG与自旋轨道耦合(SOC)。在亚纳米薄层内用单轴对角介电张量模拟2DEG光学响应,其中其$x$和$z$分量线形在自由电子和类峰贡献中分辨,结果与理论预测非常相似[M. Xie等人,Phys. Rev. B $\bf{89}$,245417(2014)]中描述的方法,该方法包括在钙钛矿界面的法线方向上限制二维电子气。特别地,$z$组分的小但有限的导电特性提供了Cu/Bi $_2$ O $_3$系统中存在2DEG的明确特征。虽然原始组成材料不具有自旋轨道耦合(SOC),但由此产生的这种状态的界面杂化诱导电子不对称波函数。这项工作证明了在非晶晶体中检测2DEG,从而可以研究其具有挑战性的界面现象,如SOC和界面-体耦合,克服了几十年来阻碍非晶材料中2DEG理解的重要进展的实验障碍。
Impact of dopant species on the interfacial trap density and mobility in amorphous In-X-Zn-O solution-processed thin-film transistors
In/Zn氧化物与各种X原子的合金化稳定了IXZO结构,但在化合物中产生电子陷阱,降低了电子迁移率。为了评估后者是否与X元素的氧亲和力或离子半径有关,通过溶胶-凝胶过程合成了几个IXZO样品,其中含有大量(14)X元素。IXZO通过XPS、SIMS、DRX和UV光谱表征,并用于制造薄膜晶体管。从TFT电学特性和低频噪声中提取的沟道迁移率和界面缺陷密度NST呈增加趋势,迁移率和NST的值呈指数关系。在In-Ga-Zn-O中获得了最高的迁移率(8.5 cm 2/Vs),并且对于Sb和Sn掺杂的IXZO获得了稍低的值,NST为约2 E12 cm 2/eV,接近于In-Zn-O参考TFT的NST。这是由于Ga、Sb和Sn的电负性高于Zn和In,它们的离子半径值接近In和Zn的离子半径值。因此,Ga,Sb和Sn在溶胶-凝胶过程中诱导的In-O和Zn-O序列的扰动较弱,而X元素具有较低的电负性和不同的离子半径。具有X = Ca、Al、Ni和Cu的TFT表现出最低的迁移率和NST > 1 E13 cm 2/eV,这很可能是由于金属或氧化物簇的形成。
We demonstrate a large-area passivation layer for graphene by mechanical transfer of ultrathin amorphous Ga$_2$O$_3$ synthesized on liquid Ga metal. A comparison of temperature-dependent electrical measurements of millimetre-scale passivated and bare graphene on SiO$_2$/Si indicate that the passivated graphene maintains its high field effect mobility desirable for applications. Surprisingly, the temperature-dependent resistivity is reduced in passivated graphene over a range of temperatures below 220 K, due to the interplay of screening of the surface optical phonon modes of the SiO$_2$ by hig…
Interfacial spin to charge conversion arises due to an electric potential perpendicular to the interface. The electric potential can be artificially induced, for example, using ferroelectric and piezoelectric thin films at the interface. An alternate way to induce the electric potential could be flexoelectric field. The flexoelectricity can be observed in all the material that either have or lack inversion symmetry, additionally no large gate bias is needed. In this experimental study, we report large spin to charge conversion (spin-Hall angle- 0.578) at Ni80Fe20/amorphous-Si interfaces attrib…
van der Waals heterostructures assembled from atomically thin crystals are ideal model systems to study spin-orbital coupled transport because they exhibit a strong interplay between spin, lattice and valley degrees of freedom that can be manipulated by strain, electric bias and proximity effects. The recently predicted spin-helical regime in graphene on transition metal dichalcogenides, in which spin and pseudospin degrees of freedom are locked together [M. Offidani et al. Phys. Rev. Lett. 119, 196801 (2017)], suggests their potential application in spintronics. Here, by deriving an Eilenberg…
Unveiling the amorphous ice layer during premelting using AFM integrating machine learning
Peking University(北京大学);University of Chinese Academy of Sciences(中国科学院大学);Wenzhou Institute, University of Chinese Academy of Sciences(中国科学院大学温州研究院);Beijing Institute of Technology(北京理工大学)