Daniel C. Ralph
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Gate-tunable electroresistance in a sliding ferroelectric tunnel junction Open
We fabricate and measure electrically-gated tunnel junctions in which the insulating barrier is a sliding van der Waals ferroelectric made from parallel-stacked bilayer hexagonal boron nitride and the electrodes are single-layer graphene. …
View article: A quantized anomalous Hall effect above 4.2 K in stacked topological insulator/magnet bilayers
A quantized anomalous Hall effect above 4.2 K in stacked topological insulator/magnet bilayers Open
Quantized anomalous Hall effects (QAHEs) occur in remarkable electronic states which possess not only quantized Hall signals but in some cases regions of dissipationless electron transport. The initial demonstrations of a QAHE in a magneti…
View article: Symmetry-controlled orbital Hall effect in IrO$_2$
Symmetry-controlled orbital Hall effect in IrO$_2$ Open
Recent discovery of orbital currents in several material platforms including light element metals has opened new possibilities for exploring novel transport phenomena and applications to spin-orbitronic devices. These orbital currents, sim…
Experimental tests of the full spin torque conductivity tensor in epitaxial IrO2 thin films Open
Unconventional spin-orbit torques arising from electric-field-generated spin currents in anisotropic materials have promising potential for spintronic applications, including for perpendicular magnetic switching in high-density memory appl…
View article: Voltage control of multiferroic magnon torque for reconfigurable logic-in-memory
Voltage control of multiferroic magnon torque for reconfigurable logic-in-memory Open
Magnons, bosonic quasiparticles carrying angular momentum, can flow through insulators for information transmission with minimal power dissipation. However, it remains challenging to develop a magnon-based logic due to the lack of efficien…
Spin-filter tunneling detection of antiferromagnetic resonance with electrically-tunable damping Open
Antiferromagnetic spintronics offers the potential for higher-frequency operations and improved insensitivity to magnetic fields compared to ferromagnetic spintronics. However, previous electrical techniques to detect antiferromagnetic dyn…
View article: Thermally generated spin current in the topological insulator Bi <sub>2</sub> Se <sub>3</sub>
Thermally generated spin current in the topological insulator Bi <sub>2</sub> Se <sub>3</sub> Open
We present measurements of thermally generated transverse spin currents in the topological insulator Bi 2 Se 3 , thereby completing measurements of interconversions among the full triad of thermal gradients, charge currents, and spin curre…
View article: Tuning the Curie temperature of a two-dimensional magnet/topological insulator heterostructure to above room temperature by epitaxial growth
Tuning the Curie temperature of a two-dimensional magnet/topological insulator heterostructure to above room temperature by epitaxial growth Open
Heterostructures of two-dimensional (2D) van der Waals (vdW) magnets and topological insulators (TI) are of substantial interest as candidate materials for efficient spin-torque switching, quantum anomalous Hall effect, and chiral spin tex…
View article: Multiferroic Magnon Spin-Torque Based Reconfigurable Logic-In-Memory
Multiferroic Magnon Spin-Torque Based Reconfigurable Logic-In-Memory Open
In-memory computing, utilizing non-volatile memories capable of performing both information storage and logic operations within the same device, holds the promise for empowering artificial intelligence (AI) with significantly reduced energ…
Exchange Bias Between van der Waals Materials: Tilted Magnetic States and Field‐Free Spin–Orbit‐Torque Switching Open
Magnetic van der Waals heterostructures provide a unique platform to study magnetism and spintronics device concepts in the 2D limit. Here, studies of exchange bias from the van der Waals antiferromagnet CrSBr acting on the van der Waals f…
View article: Multiferroic Magnon Spin-Torque Based Reconfigurable Logic-In-Memory
Multiferroic Magnon Spin-Torque Based Reconfigurable Logic-In-Memory Open
Magnons, bosonic quasiparticles carrying angular momentum, can flow through insulators for information transmission with minimal power dissipation. However, it remains challenging to develop a magnon-based logic due to the lack of efficien…
View article: Sagnac interferometry for high-sensitivity optical measurements of spin-orbit torque
Sagnac interferometry for high-sensitivity optical measurements of spin-orbit torque Open
Sagnac interferometry can provide a substantial improvement in signal-to-noise ratio compared to conventional magnetic imaging based on the magneto-optical Kerr effect. We show that this improvement is sufficient to allow quantitative meas…
View article: Tuning the Curie temperature of a 2D magnet/topological insulator heterostructure to above room temperature by epitaxial growth
Tuning the Curie temperature of a 2D magnet/topological insulator heterostructure to above room temperature by epitaxial growth Open
Heterostructures of two-dimensional (2D) van der Waals (vdW) magnets and topological insulators (TI) are of substantial interest as candidate materials for efficient spin-torque switching, quantum anomalous Hall effect, and chiral spin tex…
View article: Sagnac interferometry for high-sensitivity optical measurements of spin-orbit torque
Sagnac interferometry for high-sensitivity optical measurements of spin-orbit torque Open
Sagnac interferometry can provide a significant improvement in signal-to-noise ratio compared to conventional magnetic imaging based on the magneto-optical Kerr effect (MOKE). We show that this improvement is sufficient to allow quantitati…
View article: Symmetry Control of Unconventional Spin–Orbit Torques in IrO<sub>2</sub>
Symmetry Control of Unconventional Spin–Orbit Torques in IrO<sub>2</sub> Open
Spin–orbit torques generated by a spin current are key to magnetic switching in spintronic applications. The polarization of the spin current dictates the direction of switching required for energy‐efficient devices. Conventionally, the po…
Exchange bias between van der Waals materials: tilted magnetic states and field-free spin-orbit-torque switching Open
Magnetic van der Waals heterostructures provide a unique platform to study magnetism and spintronics device concepts in the two-dimensional limit. Here, we report studies of exchange bias from the van der Waals antiferromagnet CrSBr acting…
View article: Manipulating chiral-spin transport with ferroelectric polarization
Manipulating chiral-spin transport with ferroelectric polarization Open
A collective excitation of the spin structure in a magnetic insulator can transmit spin-angular momentum with negligible dissipation. This quantum of a spin wave, introduced more than nine decades ago, has always been manipulated through m…
Synthesis, Hole Doping, and Electrical Properties of a Semiconducting Azatriangulene-Based Covalent Organic Framework Open
Two-dimensional covalent organic frameworks (2D COFs) containing heterotriangulenes have been theoretically identified as semiconductors with tunable, Dirac-cone-like band structures, which are expected to afford high charge-carrier mobili…
View article: A puzzling insensitivity of magnon spin diffusion to the presence of 180-degree domain walls
A puzzling insensitivity of magnon spin diffusion to the presence of 180-degree domain walls Open
We present room-temperature measurements of magnon spin diffusion in epitaxial ferrimagnetic insulator MgAl 0.5 Fe 1.5 O 4 (MAFO) thin films near zero applied magnetic field where the sample forms a multi-domain state. Due to a weak uniaxi…
Cross Layer Design for the Predictive Assessment of Technology-Enabled Architectures Open
There is great interest in "end-to-end" analysis that captures how innovation at the materials, device, and/or architectural levels will impact figures of merit at the application-level. However, there are numerous combinations of devices …
Strong variation of spin-orbit torques with relative spin relaxation rates in ferrimagnets Open
Spin-orbit torques (SOTs) have been widely understood as an interfacial transfer of spin that is independent of the bulk properties of the magnetic layer. Here, we report that SOTs acting on ferrimagnetic Fe x Tb 1- x layers decrease and v…
View article: Additional Files for Thermally-generated spin current in the topological insulator Bi_2Se_3
Additional Files for Thermally-generated spin current in the topological insulator Bi_2Se_3 Open
Additional files for arXiv:2210.05636
View article: Additional Files for Thermally-generated spin current in the topological insulator Bi_2Se_3
Additional Files for Thermally-generated spin current in the topological insulator Bi_2Se_3 Open
Additional files for arXiv:2210.05636
View article: Giant room-temperature spin-orbit torque in a bismuthate superconductor
Giant room-temperature spin-orbit torque in a bismuthate superconductor Open
The emergence of artificial intelligence and machine-learning-based systems, in conjunction with the pervasive implementation of the internet of things has put a strong emphasis on the energy efficiency of computing. This has triggered res…
Strong variation of spin-orbit torques with relative spin relaxation rates in ferrimagnets Open
Spin-orbit torques (SOTs) have been widely understood as an interfacial transfer of spin that is independent of the bulk properties of the magnetic layer. Here, we report that SOTs acting on ferrimagnetic FexTb1-x layers decrease and vanis…
View article: Thermally-generated spin current in the topological insulator Bi$_2$Se$_3$
Thermally-generated spin current in the topological insulator Bi$_2$Se$_3$ Open
We complete measurements of interconversions among the full triad of thermal gradients, charge currents, and spin currents in the topological insulator Bi$_2$Se$_3$ by quantifying the efficiency with which thermal gradients can generate tr…
Gate-Tunable Anomalous Hall Effect in a 3D Topological Insulator/2D Magnet van der Waals Heterostructure Open
We demonstrate advantages of samples made by mechanical stacking of exfoliated van der Waals materials for controlling the topological surface state of a 3-dimensional topological insulator (TI) via interaction with an adjacent magnet laye…