Adjusting microwave sensing frequency through aspect ratio variation and bending repetitions in Permalloy ellipses.

The Ferromagnetic Resonance (FMR) phenomenon, marked by the selective absorption of microwave radiation by magnetic materials in the presence of a magnetic field, plays a pivotal role in the development of radar absorbing materials, high speed magnetic storage, and magnetic sensors. This process is integral for technologies requiring precise control over microwave absorption frequencies. We explored how variations in resonance fields can be effectively modulated by adjusting both the shape and stress anisotropies of magnetic materials on a flexible substrate. Utilizing polyethylene-naphthalate (PEN) as the substrate and Permalloy (Ni79Fe21, noted for its positive magnetostriction coefficient) as the magnetic component, we demonstrated that modifications in the aspect ratio and bending repetitions can significantly alter the resonance field. The results, consistent with Kittel's equation and the predictions of a uniaxial magnetic anisotropy model, underscore the potential for flexible substrates in enhancing the sensitivity and versatility of RF-based magnetic devices.

Communication Delay Outlier Detection and Compensation for Teleoperation Using Stochastic State Estimation.

There have been numerous studies attempting to overcome the limitations of current autonomous driving technologies. However, there is no doubt that it is challenging to promise integrity of safety regarding urban driving scenarios and dynamic driving environments. Among the reported countermeasures to supplement the uncertain behavior of autonomous vehicles, teleoperation of the vehicle has been introduced to deal with the disengagement of autonomous driving. However, teleoperation can lead the vehicle to unforeseen and hazardous situations from the viewpoint of wireless communication stability. In particular, communication delay outliers that severely deviate from the passive communication delay should be highlighted because they could hamper the cognition of the circumstances monitored by the teleoperator, or the control signal could be contaminated regardless of the teleoperator's intention. In this study, communication delay outliers were detected and classified based on the stochastic approach (passive delays and outliers were estimated as 98.67% and 1.33%, respectively). Results indicate that communication delay outliers can be automatically detected, independently of the real-time quality of wireless communication stability. Moreover, the proposed framework demonstrates resilience against outliers, thereby mitigating potential performance degradation.

Anisotropic Metamagnetic Spin Reorientation and Rotational Magnetocaloric Effect of Single Crystal NdAlGe.

Magnetic anisotropy strongly influences the performance of the magnetocaloric effect. We investigated the magnetocaloric properties of the NdAlGe single crystal with I41md structure. The temperature-dependent magnetization revealed significant anisotropic properties; stable antiferromagnetic transition at TN = 6 K for H//a and meta-magnetic spin reorientation at low temperature (T ≤ 5 K) within an intermediate field (H = 2 T) for H//c. During the metamagnetic spin reorientation, the abrupt change of the magnetic entropy leads to a significant magnetocaloric effect with negative magnetic entropy change (∆SM) by -13.80 J kg-1 K-1 at TC = 5.5 K for H = 5 T along the H//c axis. In addition, the antiferromagnetic state for H//a shows the inverse magnetocaloric effect(I-MCE) by positive entropy change ∆SM = 2.64 J kg-1 K-1 at TN = 6 K for H = 5 T. This giant MCE accompanied by the metamagnetic transition resulted in a significantly large relative cooling power (158 J/kg at H = 5 T) for H//c. The giant MCE and I-MCE can be applied to the rotational magnetocaloric effect (R-MCE) depending on the crystal orientations. NdAlGe exhibits rotational entropy change ∆Sc-a = -12.85 J kg-1 K at Tpeak = 7.5 K, H = 5 T. With comparison to conventional MCE materials, NdAlGe is suggested as promising candidate of R-MCE, which is a novel type of magnetic refrigeration system.

Tunable asymmetric spin wave excitation and propagation in a magnetic system with two rectangular blocks.

Asymmetric spin wave excitation and propagation are key properties to develop spin-based electronics, such as magnetic memory, spin information and logic devices. To date, such nonreciprocal effects cannot be manipulated in a system because of the geometrical magnetic configuration, while large values of asymmetry ratio are achieved. In this study, we suggest a new magnetic system with two blocks, in which the asymmetric intensity ratio can be changed between 0.276 and 1.43 by adjusting the excitation frequency between 7.8 GHz and 9.4 GHz. Because the two blocks have different widths, they have their own spin wave excitation frequency ranges. Indeed, the spin wave intensities in the two blocks, detected by the Brillouin light scattering spectrum, were observed to be frequency-dependent, yielding tuneable asymmetry ratio. Thus, this study provides a new path to enhance the application of spin waves in spin-based electronics.

Parametric excitation and mode control using an Oersted field in a NiFe nanowire.

Parametric pumping is a nonlinear wave phenomenon and a promising technique for electronic devices based on spin waves, so-called "magnonics". For parametric excitation, a magnetic nanowire system that has a built-in dc current line to produce an Oersted field is designed, and for spin wave detection, a micro-Brillouin light scattering (µ-BLS) system is used. A spin wave with a frequency of fsw = 5.6 GHz is observed when a pumping microwave with a frequency of fmw = 11.2 GHz is applied. The wave is found to be of the n = 1 width mode (n is the antinode number), and its mode changes to an edge-localized (or possibly n > 1) mode when the Oersted field (or current) varies. Joule heating effects are not observed in the pumping process. Thus, spin wave mode control by the built-in current would be a convenient and useful method to enhance the efficiency and compatibility in applications of spin-based electronics.

Phase-resolved ferromagnetic resonance using heterodyne detection method.

This paper describes a phase-resolved ferromagnetic resonance (FMR) measurement using a heterodyne method. Spin precession is driven by microwave fields and detected by 1550 nm laser light that is modulated at a frequency slightly shifted with respected to the FMR driving frequency. The evolving phase difference between the spin precession and the modulated light produces a slowly oscillating Kerr rotation signal with a phase equal to the precession phase plus a phase due to the path length difference between the excitation microwave signal and the optical signal. We estimate the accuracy of the precession phase measurement to be 0.1 rad. This heterodyne FMR detection method eliminates the need for field modulation and allows a stronger detection signal at higher intermediate frequency where the 1/f noise floor is reduced.

Transfer printing of metal nanoring and nanodot arrays for use in catalytic reactions.

Nanoscale metal ring and dot catalyst arrays are printed over large substrate areas using vertically aligned carbon-based stamps with the ring- and dot-shaped tips. The fundamental nature of these ring and dot catalysts is successfully compared by applying them in diverse electrocatalytic reactions in acidic and alkaline media.

Printable nanoscale metal ring arrays via vertically aligned carbon nanotube platforms.

This paper reports a novel and efficient strategy for fabricating sub-100 nm metal ring arrays using a simple printing process. Vertically aligned carbon nanotubes that are supported by hexagonally ordered channels of alumina matrices are used as a stamp to print nanoscale ring patterns, which is a very unique stamping platform that has never been reported. Using this strategy, uniform nanoring patterns of various metals can be directly printed onto a wide range of substrate surfaces under ambient conditions. Significantly, the size and interval of the printed nanorings can be systematically tuned by controlling the ring-shaped tip dimensions of the pristine stamps. An advanced example of these printable nanoscale metal ring arrays is explicitly embodied in this work by investigation of the plasmon resonances of metal nanorings with different sizes and intervals.

Pinning characteristics of domain wall in giant magnetoresistance spin valve stripe, consisting of a nano-wire and a circular ring.

We investigated a technique for proving the pinning behaviors of a domain wall (DW) in spin-valve stripes with artificial configurations, which consist of a nano-wire, a large pad and sharp tip at the ends of the wire, and a circular ring at the center. It was found from the GMR measurement at various positions that a DW was pinned at a ring during DW's propagation from the side of pad to the side of tip. Micromagnetic simulation revealed that the initial onion magnetic states of the ring changes continuously to final reverse onion state via counterclockwise vortex state when a counterclockwise tail-to-tail DW pass through the ring. In addition, the simulation results indicated that the magnetic states at a circular ring were determined by the type and chirality of DW. We also studied the characteristics of domain wall motion in the same configuration, when the nano-ring was replaced with square and diamond structures.

Printing of sub-100-nm metal nanodot arrays by carbon nanopost stamps.

This work reports an efficient method to fabricate hexagonally patterned metal nanodot arrays at the sub-100-nm scale, which is based on contact printing via novel nanometer-scaled stamps. Vertically aligned carbon nanoposts, supported by hexagonally ordered nanochannels of anodic aluminum oxide templates, are employed as the stamping platform to directly transfer controlled metal nanodot arrays. Using the fabrication platform, a number of patterned metal nanodot arrays made of Au, Cu, Ni, Ag, Pt, Al, and Ti can be contact-printed over large substrate areas in ambient conditions. The size, density, and interdistance of the printed nanodots are controllable with a tight correspondence to the mother stamp geometries, which can be precisely tuned by modifying the pore dimensions of the alumina matrixes. An advanced example of contact printing of metal nanoparticles is successfully demonstrated by the controlled formation of nanodot arrays in a specific area.

Current-induced domain wall nucleation and its pinning characteristics at a notch in a spin-valve nanowire.

The characteristics of domain wall (DW) pinning at a notch in a spin-valve nanowire were investigated when a DW was created by a current, flowing into a spin-valve nanowire. It was found that DW pinning at a notch is quite sensitive to the magnitude of the current and its polarity. The current-polarity dependence of DW pinning is likely due to the spin structure in the core of the DW, which is determined by an Oersted field from the current in a Cu layer. This indicates that the control of DW pinning at a notch in a nanowire can be achieved by a current acting on its own, which is an important advantage of this method, compared with field-induced DW control.