Blowing magnetic skyrmion bubbles Jiang, Wanjun; Upadhyaya, Pramey; Zhang, Wei ...
Science (American Association for the Advancement of Science),
07/2015, Letnik:
349, Številka:
6245
Journal Article
Recenzirano
Odprti dostop
The formation of soap bubbles from thin films is accompanied by topological transitions. Here we show how a magnetic topological structure, a skyrmion bubble, can be generated in a solid-state system ...in a similar manner. Using an inhomogeneous in-plane current in a system with broken inversion symmetry, we experimentally "blow" magnetic skyrmion bubbles from a geometrical constriction. The presence of a spatially divergent spin-orbit torque gives rise to instabilities of the magnetic domain structures that are reminiscent of Rayleigh-Plateau instabilities in fluid flows. We determine a phase diagram for skyrmion formation and reveal the efficient manipulation of these dynamically created skyrmions, including depinning and motion. The demonstrated current-driven transformation from stripe domains to magnetic skyrmion bubbles could lead to progress in skyrmion-based spintronics.
Oxidation of graphite produces graphite oxide, which is dispersible in water as individual platelets. After deposition onto Si/SiO2 substrates, chemical reduction produces graphene sheets. Electrical ...conductivity measurements indicate a 10000-fold increase in conductivity after chemical reduction to graphene. Tapping mode atomic force microscopy measurements show one to two layer graphene steps. Electrodes patterned onto a reduced graphite oxide film demonstrate a field effect response when the gate voltage is varied from +15 to -15 V. Temperature-dependent conductivity indicates that the graphene-like sheets exhibit semiconducting behavior.
After decades of searching for the dissipationless transport in the absence of any external magnetic field, quantum anomalous Hall effect (QAHE) was recently achieved in magnetic topological ...insulator films. However, the universal phase diagram of QAHE and its relation with quantum Hall effect (QHE) remain to be investigated. Here, we report the experimental observation of the giant longitudinal resistance peak and zero Hall conductance plateau at the coercive field in the six quintuple-layer (Cr(0.12)Bi(0.26)Sb(0.62))2Te3 film, and demonstrate the metal-to-insulator switching between two opposite QAHE plateau states up to 0.3 K. Moreover, the universal QAHE phase diagram is confirmed through the angle-dependent measurements. Our results address that the quantum phase transitions in both QAHE and QHE regimes are in the same universality class, yet the microscopic details are different. In addition, the realization of the QAHE insulating state unveils new ways to explore quantum phase-related physics and applications.
Spintronics applications of thin‐film magnets require control and design of specific magnetic properties. Exchange bias, originating from the pinning of spins in a ferromagnet by these of an ...antiferromagnet, is a part of the highly important elements for spintronics applications. Here, an exchange bias of ≈90 mT in a van der Waals ferromagnet encapsulated by two antiferromagnets at 5 K, the value of which is highly tunable by the field coolings, is reported. The non‐antisymmetric dependence of exchange bias on field cooling is explained through considering an uncompensated interfacial magnetic layer of an antiferromagnet with a noncollinear spin texture, and a weak antiferromagnetic order in the oxidized layer, at two ferromagnet/antiferromagnet interfaces. This work opens up new routes toward designing and controlling 2D spintronic devices made of atomically thin van der Waals magnets.
Two ferromagnet/antiferromagnet interfaces are formed for generating a non‐antisymmetric exchange bias, where ferromagnetic Fe3GeTe2 is coupled to antiferromagnetic CrSe with a noncollinear spin texture and oxidized Fe3GeTe2 with a weak antiferromagnetic order. This exchange bias can be manipulated with field coolings, which opens up new routes toward controlling 2D spintronic devices based on van der Waals magnets.
Topological insulators display unique properties, such as the quantum spin Hall effect, because time-reversal symmetry allows charges and spins to propagate along the edge or surface of the ...topological insulator without scattering. However, the direct manipulation of these edge/surface states is difficult because they are significantly outnumbered by bulk carriers. Here, we report experimental evidence for the modulation of these surface states by using a gate voltage to control quantum oscillations in Bi(2)Te(3) nanoribbons. Surface conduction can be significantly enhanced by the gate voltage, with the mobility and Fermi velocity reaching values as high as ~5,800 cm(2) V(-1) s(-1) and ~3.7 × 10(5) m s(-1), respectively, with up to ~51% of the total conductance being due to the surface states. We also report the first observation of h/2e periodic oscillations, suggesting the presence of time-reversed paths with the same relative zero phase at the interference point. The high surface conduction and ability to manipulate the surface states demonstrated here could lead to new applications in nanoelectronics and spintronics.
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