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Atmospheric pressure cold plasmas have great potential for surface functionalization, and the interaction between the plasmas and fibers is essential to understand the underlying physics. In this Letter, the penetration pattern and mechanism of an atmospheric pressure plasma jet (APPJ) interacting with different spacing fiber scaffolds were studied by both experiment and modeling. The intensified charge coupled device images showed that APPJ induced a radial surface streamer on the windward side of the scaffold and another axial forward streamer on the opposite side. Propagation distance of both the radial and axial streamers diminished as the spacing decreased. Similar trends were predicted by a 2D fluid model. The simulation results indicated that the high electrical field carried by the streamer head in APPJ was allowed to pass through the gap for large spacing scaffold, while it was blocked by high intensity charges at small spacing. Instead, one axial streamer was generated in the latter case. The physical insight on the penetration mechanism of plasma jet interacting with fiber array in this Letter may contribute to improve treatment uniformity of plasma technology.

Current-induced spin–orbit torque (SOT) allows for highly efficient control of magnetization for the magnetic memory and the logic application, but its high critical current density Jc limits its applications. Here, we report that the surface acoustic wave (SAW) presents a promising approach for reducing Jc in Pt/Co/Ta heterostructures with perpendicular anisotropy. By the second harmonic Hall measurements, we find that the damping-like SOT effective field is almost the same with or without SAW, implying that the reduction of Jc does not originate from the enhancement of the SOT. However, the current-induced domain wall velocity v under SAW is greatly enhanced. By fitting with the creep law under SAW, we find that lnv is linear with SAW power (P), which reveals that the effective pinning barrier is reduced linearly with increasing P. This feature can be well described by the time average of the periodically accumulated nucleation probability under SAW. The results shed light on the application of SAW-assisted SOT devices for low consumption storage.

We report on the magnetoresistance in different crystallographic directions of epitaxial ferromagnetic Fe30Co70 thin films with magnetization rotated in the film plane. A negative single crystal anisotropic magnetoresistance (SCAMR) is found when the current is along the easy magnetization axis [110], and the SCAMR can be tuned to the conventional positive one when the current flows along the hard magnetization axis [100]. This finding is explained comprehensively by a magnetocrystalline anisotropy (MCA) symmetry-adapted model expanded along the easy magnetization direction, with which the SCAMR can be represented as a MCA-independent conventional term cos 2 φ M and a series of MCA-dependent terms cos 2 n φ A ( n ≥ 1). The results show that the MCA-dependent twofold term contributes to the negative SCAMR, which cannot be used as a fingerprint of the half-metallicity. Our finding provides an approach to understand and design the magnetoresistance with ferromagnets by MCA.

Recently, electrical switching of interface states in nonferromagnet/ferromagnet (FM)/antiferromagnet (AFM) heterostructure using spin–orbit torque (SOT) is promising due to its high efficiency, zero magnetic field, and multilevel memory state. However, the reversal mechanism of the AFM interface state is still unclear. In this work, we explained the bipolar current switching of the AFM interface state at zero magnetic field by spin–orbit torque (SOT) in a perpendicularly magnetized Pt/Co/IrMn multilayer. By considering symmetry, we reveal that the mechanism behind the AFM interface bipolar current switching is consistent with FM layers perpendicularly switching induced by SOT. The distinct AFM bipolar current switching by SOT is contributed to the symmetry broken by adjacent FM interface coupling. Under such broken symmetry, the antiparallel interface configuration (AP) between FM and AFM could be switched to parallel configuration (P) for both positive and negative currents; however, P is only allowed to be switched to the AFM multiple domain configuration (M), instead of AP. Our result will be helpful for the formulation of a comprehensive understanding of AFM switching induced by SOT and for the development of the interface AFM spintronic devices.

The microscopic mechanism for the current-induced spin–orbit torque (SOT) in magnetic heterostructures is still under debate. The accurate measurement of SOT effective fields and their thickness dependence is the basis for understanding this issue. In this work, we measured the SOT effective fields for Pt/NiFe bilayers by utilizing the harmonic longitudinal voltage (HLV) method with a Wheatstone bridge structure. Benefiting from the elimination of the linear resistance in the bridge structure and the large magnetoresistance difference resulting from the large length–width ratio of the bridge element, we achieved very high measurement accuracy for both field-like and damping-like effective fields in the Pt/NiFe bilayers. On this basis, we demonstrated the possibility of the SOT measurement with a relatively low current density (∼109 A/m2) by utilizing the HLV method with a Wheatstone bridge structure and found that the method we proposed is also applicable to the Pt/CoFeB system with a low anisotropic magnetoresistance ratio.

In contrast to traditional concepts that eliminate magnetic impurities to achieve larger thermoelectric efficiencies, we report an enhanced thermoelectric efficiency for Cu through doping with the magnetic impurity Co. With doping concentrations from 15% to 30%, the amplitude of the Seebeck coefficient increases from 1.90 μV/K up to 16.3 μV/K, which greatly enhances the thermoelectric efficiency (i.e., power factor). Measuring the magnetoresistance and magnetothermoelectric powers at different temperatures indicates that the enhancement of thermoelectric efficiency is a result of spin-dependent scattering from Co nanoparticles, which are less sensitive to the superparamagnetic transitions. Our finding illustrates a path for the use of nanomagnets to develop potential thermoelectric materials.

Magnetization switching via charge current induced spin-orbit torques (SOTs) in heavy metal/ferromagnetic metal/heavy metal heterostructures has become an important issue due to its potential applications in high stability and low energy dissipation spintronic devices. In this work, based on a Pt/Co/Ta structure with perpendicular magnetic anisotropy (PMA), we report the effect of inserting a non-metal C interlayer between Co and Ta on the current-induced magnetization switching. A series of measurements based on the extraordinary Hall effect were carried out to investigate the difference of the anisotropy field, switching field, and damping-like and field-like SOT-induced effective fields as well as the current-induced spin Hall effect (SHE) torque after C decoration. The results show that PMA can be reduced by C decoration and the ratio of the effective SHE torque per unit current density and anisotropy field plays an essential role in the switching efficiency. In addition, the obtained switching curren...

To control the semiconductor device under low magnetic field is still a great challenge for semiconductor magnetoelectronics. In this work, we report the observation of the magneto-photogalvanic effect in periodic GaAs dot arrays. With an increase in magnetic field from 0 to 1500 Oe, the photovoltage increases linearly for a wide temperature range from 80 to 430 K. Compared with GaAs without the dot arrays, periodic GaAs dot arrays have a hundredfold increase of the magnetic-field-modulated photovoltage at room temperature. By changing the magnetic field orientation, the angular dependence of photovoltage reveals that the magneto-photogalvanic effect stems from the Hall electric field caused by optical current, and the enhancement of magneto-photogalvanic effect is attributed to the p-n junction coupling between GaAs dots. When the coupling between the GaAs dots is broken at the high temperatures, i.e., T = 430 K, we demonstrate that the enhancement effect disappears as expected. Our results not only illu...

Mechanical transfer of GaN-based heterostructures using h-BN as the release layer [Y. Kobayashi, K. Kumakura, T. Akasaka, and T. Makimoto, Nature 484, 223 (2012)] has promising applications for the next-generation optoelectronic devices. We investigate such transfer mechanism by mapping out the interlayer sliding energy landscape at each interface of a model heterostructure composed of GaN/BN/substrate together with the reference case of BN/BN interlayer sliding. The calculated results based on density functional theory find a nearly free sliding path for BN/BN, while a slightly higher energy barrier is predicted for hetero-interfaces of strained GaN/BN and BN/graphene substrate. The unstrained GaN/BN interface facilitates an easier peel-off of GaN from the BN layer. Thus, the sliding mechanism, which can also be described by the registry index model, shows dominance of the electrostatic interaction terms associated with the constituent layers of the system, though the van der Waals interaction term seems...