Magnetic skyrmions in chiral magnets with the Dzyaloshinskii-Moriya interaction have received intensive attention because of their potential in prospective applications. Here, we theoretically demonstrate that another novel spin texture in chiral magnetsthe chiral strip-domain wall (SDW)-can generate a deep one-dimensional potential well of magnetic origin. We show by micromagnetic simulations that the potential well caused by a SDW can serve as an internal channel to guide spin-wave (SW) propagation, which makes the ultrathin chiral magnet including the SDW become a reconfigurable self-cladding optic-fiber-like magnonic waveguide with a graded refractive index. Furthermore, we design logical NOT and NAND gates based on the statemodulated transmission property of the magnonic waveguide. We also reveal that a SDW can be reliably written into the gate arms using the Slonczewski spin torque. Finally, prospective applications of the observed potential well in other fields are envisioned. This work is expected to open new possibilities for SW guiding and manipulation in ultrathin magnetic nanostructures as well as to help shape the field of beam magnonics.

Skyrmions and domain walls are typical spin textures of significant technological relevance to magnetic memory and logic applications, where they are used as carriers of information. The unique topology of skyrmions makes them to display distinct dynamical properties compared to domain walls. Some studies have demonstrated that the two topologically inequivalent magnetic objects could be interconverted by cleverly designed geometric structures. Here, we numerically address the skyrmion-domain wall collision in a magnetic racetrack by introducing relative motion between the two objects based on a specially designed junction. An electric current serves as the driving force that moves a skyrmion toward a trapped domain-wall pair. We observe different types of collision dynamics by changing the driving parameters. Most importantly, the domain wall modulation of skyrmion  Author to whom correspondence should be addressed: Y. Zhou (E-mail: yanzhou@hku.hk) 2 transport is realized in this system, allowing a set of domain wall-gated logical NOT, NAND, and NOR gates to be constructed. By providing a promising logic architecture that is fully compatible with racetrack memories, this work is expected to speed up the development of skyrmion-based magnetic computation.

Spin-wave devices hold great promise to be used in future information processing. Manipulation of spin-wave propagation inside the submicrometer waveguides is at the core of promoting the practical application of these devices. Just as in today's silicon-based chips, bending of the building blocks cannot be avoided in real spin-wave circuits. Here, we examine spin-wave transport in bended magnonic waveguides at the submicron scale using micromagnetic simulations. It is seen that the impact of the bend is relevant to the frequency of the passing spin wave. At the lowest frequencies, the spin wave continuously follows the waveguide in the propagation process. At the higher frequencies, however the bend acts as a mode converter for the passing spin wave, causing zigzag-like propagation path formed in the waveguide behind the bend. Additionally, we demonstrate a logic-NOT gate based on such a waveguide, which could be combined to perform logic-NAND operation.

Stoichiometric single-crystalline TiO2 thin films were grown on SrTi0.99Nb0.01O3 (Nb:STO) substrates by oxygen plasma-assisted molecular beam epitaxy. The Pt∕TiO2∕Nb:STO∕Pt devices showed extremely weak resistance switching hysteresis without applying reverse bias. However, when the reverse bias increased above −2V, the hysteresis became more and more prominent. Further, it was found that the low (high) resistance state can be set by applying sufficient reverse (forward) bias. The origin of the reverse-bias-induced bipolar switching behavior should be attributed to the modulation of Schottky-like barrier width by electrochemical migration of oxygen vacancies.

Single crystal β-MnO 2 films have been epitaxially grown on (001) LaAlO 3 and (001) MgO substrates by using plasma-assisted molecular beam epitaxy. On the basis of reflective high energy electron diffraction, X-ray diffraction, Raman spectroscopy, and X-ray photoemission spectroscopy, the films are confirmed to be β-MnO 2 with slight oxygen vacancies resulting in coexistence of Mn 3+ and Mn 4+ . These films are ferromagnetic at room temperature, which is reckoned to result from new forms of exchange interaction in MnO 2 due to coexisting Mn 3+ and Mn 4+ . The films on various substrates show different magnetic properties at 5 K attributable to different spin configurations between these films, which supports Yoshimori's theoretical prediction that an applied stress can vary the screw spin configuration. Two potential interaction mechanisms are proposed regarding the origins of the observed magnetic properties.

Room-temperature ferromagnetism in (Mn, N)-codoped TiO 2 films grown by plasma assisted molecular beam epitaxy J. Appl. Phys.

Articles you may be interested inRoom-temperature ferromagnetism in (Mn, N)-codoped TiO 2 films grown by plasma assisted molecular beam epitaxy J. Appl. Phys.

Based on micromagnetic simulations and model calculations, we demonstrate that degenerate well and barrier magnon modes can exist concurrently in a single magnetic waveguide magnetized perpendicularly to the long axis in a broad frequency band, corresponding to copropagating edge and centre spin waves, respectively. The dispersion relations of these magnon modes clearly show that the edge and centre modes possess much different wave characteristics. By tailoring the antenna size, the edge mode can be selectively activated. If the antenna is sufficiently narrow, both the edge and centre modes are excited with considerable efficiency and propagate along the waveguide. By roughening the lateral boundary of the waveguide, the characteristics of the relevant channel can be easily engineered. Moreover, the coupling of the edge and centre modes can be conveniently controlled by scaling the width of the waveguide. For a wide waveguide with a narrow antenna, the edge and centre modes travel relatively independently in spatially-separate channels, whereas for a narrow strip, these modes strongly superpose in space. These discoveries might find potential applications in emerging magnonic devices