Bei Ding

A Centrosymmetric Hexagonal Magnet with Superstable Biskyrmion Magnetic Nanodomains in a Wide Temperature Range of 100–340 K

Superstable biskyrmion magnetic nanodomains are experimentally observed for the first time in a hexagonal MnNiGa, a common and easily produced centrosymmetric material. The biskyrmion states in MnNiGa thin plates, as determined by the combination of in situ Lorentz transmission electron microscopy images, magnetoresistivity, and topological Hall effect measurements, are surprisingly stable over a broad temperature range of 100-340 K.

Observation of Various and Spontaneous Magnetic Skyrmionic Bubbles at Room Temperature in a Frustrated Kagome Magnet with Uniaxial Magnetic Anisotropy

The quest for materials hosting topologically protected skyrmionic spin textures continues to be fueled by the promise of novel devices. Although many materials have demonstrated the existence of such spin textures, major challenges remain to be addressed before devices based on magnetic skyrmions can be realized. For example, being able to create and manipulate skyrmionic spin textures at room temperature is of great importance for further technological applications because they can adapt to various external stimuli acting as information carriers in spintronic devices. Here, the first observation of skyrmionic magnetic bubbles with variable topological spin textures formed at room temperature in a frustrated kagome Fe3 Sn2 magnet with uniaxial magnetic anisotropy is reported. The magnetization dynamics are investigated using in situ Lorentz transmission electron microscopy, revealing that the transformation between different magnetic bubbles and domains is via the motion of Bloch lines driven by an applied external magnetic field. These results demonstrate that Fe3 Sn2 facilitates a unique magnetic control of topological spin textures at room temperature, making it a promising candidate for further skyrmion-based spintronic devices.

Large and Anisotropic Linear Magnetoresistance in Single Crystals of Black Phosphorus Arising From Mobility Fluctuations

Black Phosphorus (BP) is presently attracting immense research interest on the global level due to its high mobility and suitable band gap for potential application in optoelectronics and flexible devices. It was theoretically predicted that BP has a large direction-dependent electrical and magnetotransport anisotropy. Investigations on magnetotransport of BP may therefore provide a new platform for studying the nature of electron transport in layered materials. However, to the best of our knowledge, magnetotransport studies, especially the anisotropic magnetoresistance (MR) effect in layered BP, are rarely reported. Here, we report a large linear MR up to 510% at a magnetic field of 7 Tesla in single crystals of BP. Analysis of the temperature and angle dependence of MR revealed that the large linear MR in our sample originates from mobility fluctuations. Furthermore, we reveal that the large linear MR of layered BP in fact follows a three-dimensional behavior rather than a two-dimensional one. Our results have implications to both the fundamental understanding and magnetoresistive device applications of BP.

Real-Space Observation of Nonvolatile Zero-Field Biskyrmion Lattice Generation in MnNiGa Magnet

Magnetic skyrmions, particular those without the support of external magnetic fields over a wide temperature region, are promising as alternative spintronic units to overcome the fundamental size limitation of conventional magnetic bits. In this study, we use in situ Lorentz microscope to directly demonstrate the generation and sustainability of robust biskyrmion lattice at zero magnetic field over a wide temperature range of 16-338 K in MnNiGa alloy. This procedure includes a simple field-cooling manipulation from 360 K (higher than Curie temperature TC ∼ 350 K), where topological transition easily occurs by adapting the short-range magnetic clusters under a certain magnetic field. The biskyrmion phase is favored upon cooling below TC. Once they are generated, the robust high-density biskyrmions persist even after removing the external magnetic field due to the topological protection and the increased energy barrier.

Transition from Anomalous Hall Effect to Topological Hall Effect in Hexagonal Non-Collinear Magnet Mn 3 Ga

We report experimental observation of large anomalous Hall effect exhibited in non-collinear triangular antiferromagnet D019-type Mn3Ga with coplanar spin structure at temperatures higher than 100 K. The value of anomalous Hall resistivity increases with increasing temperature, which reaches 1.25 μΩ · cm at a low field of ~300 Oe at room temperature. The corresponding room-temperature anomalous Hall conductivity is about 17 (Ω · cm)−1. Most interestingly, as temperature falls below 100 K, a temperature-independent topological-like Hall effect was observed. The maximum peak value of topological Hall resistivity is about 0.255 μΩ · cm. The appearance of the topological Hall effect is attributed to the change of spin texture as a result of weak structural distortion from hexagonal to orthorhombic symmetry in Mn3Ga. Present study suggests that Mn3Ga shows promising possibility to be antiferromagnetic spintronics or topological Hall effect-based data storage devices.

Large topological Hall effect in nonchiral hexagonal MnNiGa films

We report a systematic study of the magnetic and transport properties of magnetron sputtered nonchiral hexagonal MnNiGa films on the thermally oxidized Si substrates as a function of film thickness. A large topological Hall effect (THE) is observed, and its magnitude increases correspondingly with increasing the film thickness. The large THE appears in a very wide temperature range of 10 K–300 K in a magnetic field region where the field-dependent Hall resistivity largely deviates from the magnetization. Moreover, the measurements on the cubic MnNiGa films do not show any evidence of the existence of THE. These results indicate that the non-collinear spin configurations from geometrical frustration of Mn moments are the likely origin of the observed large THE in hexagonal MnNiGa films.

Creation of Single Chain of Nanoscale Skyrmion Bubbles with Record-High Temperature Stability in a Geometrically Confined Nanostripe

Nanoscale topologically nontrivial spin textures, such as magnetic skyrmions, have been identified as promising candidates for the transport and storage of information for spintronic applications, notably magnetic racetrack memory devices. The design and realization of a single skyrmion chain at room temperature (RT) and above in the low-dimensional nanostructures are of great importance for future practical applications. Here, we report the creation of a single skyrmion bubble chain in a geometrically confined Fe3Sn2 nanostripe with a width comparable to the featured size of a skyrmion bubble. Systematic investigations on the thermal stability have revealed that the single chain of skyrmion bubbles can keep stable at temperatures varying from RT up to a record-high temperature of 630 K. This extreme stability can be ascribed to the weak temperature-dependent magnetic anisotropy and the formation of edge states at the boundaries of the nanostripes. The realization of the highly stable skyrmion bubble chain in a geometrically confined nanostructure is a very important step toward the application of skyrmion-based spintronic devices.

Large topological hall effect observed in tetragonal Mn2PtSn Heusler thin film

Tetragonal Mn-Pt-Sn Heusler compounds have been of interest because they enable magnetic antiskyrmion phases, which can potentially lead to low energy cost spintronic device applications. We report the synthesis and systematic study of the magnetic and transport properties of magnetron sputtered tetragonal Mn2PtSn thin films on the thermally oxidized Si substrates. We have observed a large topological Hall resistivity up to 0.57 μΩ cm around 150 K, which is the largest value among the Mn-based metallic materials so far. Moreover, the large topological Hall effect (THE) appears in a very wide temperature range of 10 K–300 K in a magnetic field region where the field-dependent Hall resistivity largely deviates from the magnetization. The large THE indicated here may also provide pathways towards realizing the magnetic antiskyrmions in tetragonal Mn2PtSn thin films.Tetragonal Mn-Pt-Sn Heusler compounds have been of interest because they enable magnetic antiskyrmion phases, which can potentially lead to low energy cost spintronic device applications. We report the synthesis and systematic study of the magnetic and transport properties of magnetron sputtered tetragonal Mn2PtSn thin films on the thermally oxidized Si substrates. We have observed a large topological Hall resistivity up to 0.57 μΩ cm around 150 K, which is the largest value among the Mn-based metallic materials so far. Moreover, the large topological Hall effect (THE) appears in a very wide temperature range of 10 K–300 K in a magnetic field region where the field-dependent Hall resistivity largely deviates from the magnetization. The large THE indicated here may also provide pathways towards realizing the magnetic antiskyrmions in tetragonal Mn2PtSn thin films.

Crystal-orientation dependence of magnetic domain structures in the skyrmion-hosting magnets MnNiGa

We explore how crystal orientation affects the magnetic domains in the skyrmion-hosting MnNiGa magnets by Lorentz transmission electron microscopy. As a result, we found that the formation of topological spin textures depended significantly on both the crystal orientation and magnetic field. When the magnetic field was slightly tilted 5° from the easy-axis [001], the topological trivial bubbles were observed, while in a large tilted angle of 31° from the [001] direction, the magnetic biskyrmions were observed. Our results indicate that the magnetic domains are very sensitive to the orientation of the magnetic field with respect to the easy-axis in the centrosymmetric skyrmion-hosting magnets.