The spin-wave induced domain wall motion in a nanostrip with perpendicular magnetic anisotropy is studied. It is found that the domain wall can move either in the same direction or in the opposite direction to that of spin-wave propagation depending on whether the spin wave is reflected by the wall or transmitted through the wall. A magnonic momentum transfer mechanism is proposed and, together with the magnonic spin-transfer torque, a one-dimensional phenomenal model is constructed. The wall motion calculated based on this model is in qualitative agreement with micromagnetic simulations, showing that the model can describe the characteristics of spin-wave-induced wall motion and, especially, the wall motion direction.The magnetic domain wall motion induced by spin-transfer torque (STT) from a spin-polarized electrical current has attracted growing interest because of its fundamental relevance and potential applications in spintronic devices such as Racetrack memory and logic devices. 1-3 It is widely recognized that there are two types of STT acting on the wall when a spin-polarized current flows through it, namely the adiabatic STT and nonadiabatic STT. 4,5 The adiabatic STT comes from the adiabatic reversal of conduction electron spins, which induces a reaction torque on the wall as required by the conservation of angular momentum. 6 However, the origin of nonadiabatic STT still remains controversial. There are many contributions to this torque, such as spin-orbit interactions, spin-flip scattering, etc. 7-9 When the domain wall is narrow, the momentum transfer due to the electron reflection by the wall also contributes to the nonadiabatic STT. 10 The influence of the adiabatic and nonadiabatic STT on the wall motion is different. The adiabatic STT plays a more important role at the initial motion of the wall. It provides an initial velocity and causes the wall to move, but finally, it is balanced by an internal restoring torque and the wall motion ceases. 6 In contrast, the nonadiabatic STT behaves like a magnetic field and can sustain a steady-state wall motion. 5 Recently, the noncharge-based spin current, magnonic spin current, is proposed 11 and experimentally demonstrated. 12 Similar to the spin-polarized electrical current, the magnonic spin current also leads to the STT in the magnet and can be exploited to control the spin structures, including the displacement of the domain wall. Hinzke et al. 13 first demonstrated theoretically that a single domain wall in a nanowire can be displaced by a magnonic spin current due to the temperature gradient. Yan et al. 14 showed that a spin wave excited by a microwave field can also drive a wall motion. They suggested that the mechanism of wall motion is the spin transfer torque resulting from the angular momentum transfer between the magnons and the local magnetization in the wall. As a magnon moves across the wall, its angular moment is changed by 2h which is absorbed by the wall, making the wall propagate in the opposite direction to that of the magnon. It is wo...

The early detection and diagnosis of malignant colorectal tumors enables the initiation of early-stage therapy and can significantly increase the survival rate and post-treatment quality of life among cancer patients. Hyperspectral imaging (HSI) is recognized as a powerful tool for noninvasive cancer detection. In the gastrointestinal field, most of the studies on HSI have involved ex vivo biopsies or resected tissues. In the present study, we aimed to assess the difference in the in vivo spectral reflectance of malignant colorectal tumors and normal mucosa. A total of 21 colorectal tumors or adenomatous polyps from 12 patients at Shanghai Zhongshan Hospital were examined using a flexible hyperspectral (HS) colonoscopy system that can obtain in vivo HS images of the colorectal mucosa. We determined the optimal wavelengths for differentiating tumors from normal tissue based on these recorded images. The application of the determined wavelengths in spectral imaging in clinical trials indicated that such a clinical support system comprising a flexible HS colonoscopy unit and band selection unit is useful for outlining the tumor region and enhancing the display of the mucosa microvascular pattern in vivo.

The spin wave propagation and the spin-wave induced domain wall motion in a nanostrip with a Bloch domain wall are studied. The spin-wave dispersion relation and the transmission coefficients across the wall are derived analytically. A one-dimensional model for the domain wall motion is constructed. It is found that the spin wave can drive the wall to move either in the same direction or in the opposite direction to that of spin-wave propagation depending on the transmission coefficient. The transmitted magnons drag the wall moving backward without inertia by the adiabatic and nonadiabatic spin-transfer torques, while the reflected magnons push the wall moving forward by the linear momentum transfer torque.

Tuning the magneto optical response and magnetic dynamics are key elements in designing magnetic metamaterials and devices. This theoretical study uncovers a highly effective way of controlling the magnetic permeability via shaping the magnonic properties of coupled magnetic waveguides separated by a nonmagnetic spacer with strong spin–orbit interaction (SOI). We demonstrate how a spacer charge current leads to enhancement of magnetic damping in one waveguide and a decrease in the other, constituting a bias-controlled magnetic parity–time (PT) symmetric system at the verge of the exceptional point where magnetic gains/losses are balanced. We find phenomena inherent to PT-symmetric systems and SOI-driven interfacial structures, including field-controlled magnon power oscillations, nonreciprocal propagation, magnon trapping and enhancement as well as an increased sensitivity to perturbations and abrupt spin reversal. The results point to a new route for designing magnonic waveguides and microstructures with enhanced magnetic response.