Search for: All records

Collinear antiferromagnetic (AFM) materials have the unique promise of no stray fields, displaying ultrafast dynamics, and being robust against perturbation fields which motivate the extensive research of antiferromagnetic spintronics. However, the detection of antiferromagnetic order poses formidable challenges. Here, we report the electrical detection of colinear antiferromagnetism in all-epitaxial RuO2/MgO/RuO2 tunnel junctions (TJ) using spin-flop tunneling anisotropic magnetoresistance (TAMR). We measured a TAMR ratio of around 60% at room temperature, which arises from the switching between the parallel and perpendicular configurations of the adjacent collinear AFM state. Furthermore, we carried out angular-dependent measurements using this antiferromagnetic tunnel junction (AFM-TJ) and showed that the magnitude of anisotropic longitudinal magnetoresistance in the AFM-TJ can be controlled by the direction of an external magnetic field. First principles electronic structure calculations corroborate that the collinear antiferromagnetic TJ may produce a substantially large TAMR ratio. The emergence of resonant interfacial states, combined with the tunneling transmission through the MgO barrier and the substantial spin-orbit coupling (SOC) strength of Ru, especially when augmented by oxygen doping, leads to the significant enhancement observed in the tunneling anisotropic magnetoresistance (TAMR). Our work not only propels antiferromagnetic materials to the forefront of spintronic device innovation but also unveils a novel paradigm for electrically controlled antiferromagnetic spintronics, auguring transformative advancements in high-speed, low-energy information devices. 

Abstract Topological insulators (TI) and magnetic topological insulators (MTI) can apply highly efficient spin‐orbit torque (SOT) and manipulate the magnetization with their unique topological surface states (TSS) with ultrahigh efficiency. Here, efficient SOT switching of a hard MTI, V‐doped (Bi,Sb)₂Te₃(VBST), with a large coercive field that can prevent the influence of an external magnetic field, is demonstrated. A giant switched anomalous Hall resistance of 9.2 kΩ is realized, among the largest of all SOT systems, which makes the Hall channel a good readout and eliminates the need to fabricate complicated magnetic tunnel junction (MTJ) structures. The SOT switching current density can be reduced to 2.8 × 10⁵ A cm⁻², indicating its high efficiency. Moreover, as the Fermi level is moved away from the Dirac point by both gate and composition tuning, VBST exhibits a transition from edge‐state‐mediated to surface‐state‐mediated transport, thus enhancing the SOT effective field to (1.56 ± 0.12) × 10⁻⁶ T A⁻¹ cm²and the interfacial charge‐to‐spin conversion efficiency to 3.9 ± 0.3 nm⁻¹. The findings establish VBST as an extraordinary candidate for energy‐efficient magnetic memory devices. 

Abstract The inelastic scattering length ( L s ) is a length scale of fundamental importance in condensed matters due to the relationship between inelastic scattering and quantum dephasing. In quantum anomalous Hall (QAH) materials, the mesoscopic length scale L s plays an instrumental role in determining transport properties. Here we examine L s in three regimes of the QAH system with distinct transport behaviors: the QAH, quantum critical, and insulating regimes. Although the resistance changes by five orders of magnitude when tuning between these distinct electronic phases, scaling analyses indicate a universal L s among all regimes. Finally, mesoscopic scaled devices with sizes on the order of L s were fabricated, enabling the direct detection of the value of L s in QAH samples. Our results unveil the fundamental length scale that governs the transport behavior of QAH materials. 

The electric field manipulates the spin chirality and skyrmion motion direction in a magnetic heterostructure. 

Abstract From elementary particles to cosmological structures, topological solitons are ubiquitous nonlinear excitations valued for their robustness and complex interactions. In magnetism, solitons such as skyrmions and antiskyrmions behave analogously to particles and antiparticles, typically annihilating in pairs in accordance with topological conservation laws. Here the stripe‐to‐skyrmion transition is experimentally observed and a model for a skyrmion–antiskyrmion–skyrmion intertwined state is introduced, in which the central antiskyrmion is annihilated, leading to an increase in the local topological number. Because this transition occurs repeatedly across the film, the cumulative effect produces a global increase in the total topological charge. This model reflects a breakdown of topological protection in isotropic Dzyaloshinskii–Moriya interaction (DMI) materials, where symmetry constraints render the antiskyrmion energetically unstable and thermally activated. Using micromagnetic simulations and minimum‐energy‐path calculations, the antiskyrmion is identified as a transient, metastable excitation. To highlight its functional potential, this stripe‐to‐skyrmion transition within a Hall device is exploited to generate stochastic bitstreams, which are subsequently used in a proof‐of‐concept probabilistic computing demonstration. These results contribute to the understanding of topological spin‐texture dynamics and suggest opportunities for leveraging their transient behavior in probabilistic computing architectures.