Quantum Sensing of Spin Dynamics Using Boron-Vacancy Centers in Hexagonal Boron Nitride.

Spin defects embedded in solid-state systems are appealing for quantum sensing of materials and for quantum science and engineering. The spin-sensitive photoluminescence of optically active spin defects in Van der Waals based materials, such as the boron-vacancy (V_{B}^{-}) center in hexagonal boron nitride, enables its application as a quantum sensor to detect weak, spatially localized magnetic static and dynamic fields. However, the utility of V_{B}^{-} centers to probe spin dynamics in magnetic systems has yet to be demonstrated; this is essential to establish the V_{B}^{-} as a modular sensing platform that can be seamlessly integrated with emergent quantum materials to probe a wide range of static and dynamic phenomena.

Roadmap on nanoscale magnetic resonance imaging.

The field of nanoscale magnetic resonance imaging (NanoMRI) was started 30 years ago. It was motivated by the desire to image single molecules and molecular assemblies, such as proteins and virus particles, with near-atomic spatial resolution and on a length scale of 100 nm. Over the years, the NanoMRI field has also expanded to include the goal of useful high-resolution nuclear magnetic resonance (NMR) spectroscopy of molecules under ambient conditions, including samples up to the micron-scale.

Strong on-Chip Microwave Photon-Magnon Coupling Using Ultralow-Damping Epitaxial YFeO Films at 2 K.

YFeO is arguably the best magnetic material for magnonic quantum information science (QIS) because of its extremely low damping. We report ultralow damping at 2 K in epitaxial YFeO thin films grown on a diamagnetic YScGaO substrate that contains no rare-earth elements. Using these ultralow damping YIG films, we demonstrate for the first time strong coupling between magnons in patterned YIG thin films and microwave photons in a superconducting Nb resonator.

Enhancing Perpendicular Magnetic Anisotropy in Garnet Ferrimagnet by Interfacing with Few-Layer WTe.

Engineering magnetic anisotropy in a ferro- or ferrimagnetic (FM) thin film is crucial in a spintronic device. One way to modify the magnetic anisotropy is through the surface of the FM thin film. Here, we report the emergence of a perpendicular magnetic anisotropy (PMA) induced by interfacial interactions in a heterostructure comprised of a garnet ferrimagnet, YFeO (YIG), and a low-symmetry, high spin-orbit coupling (SOC) transition metal dichalcogenide, WTe.

Spin-Orbit Torque Nano-oscillators by Dipole-Field-Localized Spin Wave Modes.

We demonstrate a high-quality spin-orbit torque nano-oscillator comprised of spin wave modes confined by the magnetic field by the strongly inhomogeneous dipole field of a nearby micromagnet. This approach enables variable spatial confinement and systematic tuning of magnon spectrum and spectral separations for studying the impact of multimode interactions on auto-oscillations. We find these dipole-field-localized spin wave modes exhibit good characteristic properties as auto-oscillators─narrow line width and large amplitude─while persisting up to room temperature.

Broadband multi-magnon relaxometry using a quantum spin sensor for high frequency ferromagnetic dynamics sensing.

Development of sensitive local probes of magnon dynamics is essential to further understand the physical processes that govern magnon generation, propagation, scattering, and relaxation. Quantum spin sensors like the NV center in diamond have long spin lifetimes and their relaxation can be used to sense magnetic field noise at gigahertz frequencies. Thus far, NV sensing of ferromagnetic dynamics has been constrained to the case where the NV spin is resonant with a magnon mode in the sample meaning that the NV frequency provides an upper bound to detection.

Nonlocal Uniform-Mode Ferromagnetic Resonance Spin Pumping.

Nonlocal spin transport using lateral structures is attractive for spintronic devices. Typically, a spin current is generated by a ferromagnetic (FM) or a heavy metal (HM) electrode in a nonlocal structure, which can be detected by another FM or HM electrode. Here, we report a new nonlocal spin injection scheme using uniform-mode ferromagnetic resonance (FMR) spin pumping in Pt/YFeO (YIG) lateral structures.

Interfacial Rashba-Effect-Induced Anisotropy in Nonmagnetic-Material-Ferrimagnetic-Insulator Bilayers.

Interfacial magnetic anisotropy in magnetic insulators has been largely unexplored. Recently, interface-induced skyrmions and electrical control of magnetization have been discovered in insulator-based heterostructures, which demand a thorough understanding of interfacial interactions in these materials. We observe a substantial, tunable interfacial magnetic anisotropy between Tm_{3}Fe_{5}O_{12} epitaxial thin films and fifteen nonmagnetic materials spanning a significant portion of the periodic table, which we attribute to Rashba spin-orbit coupling.

Fundamental Spin Interactions Underlying the Magnetic Anisotropy in the Kitaev Ferromagnet CrI_{3}.

We lay the foundation for determining the microscopic spin interactions in two-dimensional (2D) ferromagnets by combining angle-dependent ferromagnetic resonance (FMR) experiments on high quality CrI_{3} single crystals with theoretical modeling based on symmetries. We discover that the Kitaev interaction is the strongest in this material with K∼-5.2  meV, 25 times larger than the Heisenberg exchange J∼-0.

Spin-Hall Topological Hall Effect in Highly Tunable Pt/Ferrimagnetic-Insulator Bilayers.

Electrical detection of topological magnetic textures such as skyrmions is currently limited to conducting materials. Although magnetic insulators offer key advantages for skyrmion technologies with high speed and low loss, they have not yet been explored electrically. Here, we report a prominent topological Hall effect in Pt/TmFeO bilayers, where the pristine TmFeO epitaxial films down to 1.

Voltage-driven, local, and efficient excitation of nitrogen-vacancy centers in diamond.

Magnetic sensing technology has found widespread application in a diverse set of industries including transportation, medicine, and resource exploration. These uses often require highly sensitive instruments to measure the extremely small magnetic fields involved, relying on difficult-to-integrate superconducting quantum interference devices and spin-exchange relaxation-free magnetometers. A potential alternative, nitrogen-vacancy (NV) centers in diamond, has shown great potential as a high-sensitivity and high-resolution magnetic sensor capable of operating in an unshielded, room-temperature environment.

A Novel Small-Specimen Planar Biaxial Testing System With Full In-Plane Deformation Control.

Simulations of soft tissues require accurate and robust constitutive models, whose form is derived from carefully designed experimental studies. For such investigations of membranes or thin specimens, planar biaxial systems have been used extensively. Yet, all such systems remain limited in their ability to: (1) fully prescribe in-plane deformation gradient tensor F2D, (2) ensure homogeneity of the applied deformation, and (3) be able to accommodate sufficiently small specimens to ensure a reasonable degree of material homogeneity.

Metallic ferromagnetic films with magnetic damping under 1.4 × 10.

Low-damping magnetic materials have been widely used in microwave and spintronic applications because of their low energy loss and high sensitivity. While the Gilbert damping constant can reach 10 to 10 in some insulating ferromagnets, metallic ferromagnets generally have larger damping due to magnon scattering by conduction electrons. Meanwhile, low-damping metallic ferromagnets are desired for charge-based spintronic devices.

Electron Paramagnetic Resonance of a Single NV Nanodiamond Attached to an Individual Biomolecule.

Electron paramagnetic resonance (EPR), an established and powerful methodology for studying atomic-scale biomolecular structure and dynamics, typically requires in excess of 10(12) labeled biomolecules. Single-molecule measurements provide improved insights into heterogeneous behaviors that can be masked in ensemble measurements and are often essential for illuminating the molecular mechanisms behind the function of a biomolecule. Here, we report EPR measurements of a single labeled biomolecule.

Nanofiber-based paramagnetic probes for rapid, real-time biomedical oximetry.

EPR (electron paramagnetic resonance) based biological oximetry is a powerful tool that accurately and repeatedly measures tissue oxygen levels. In vivo determination of oxygen in tissues is crucial for the diagnosis and treatment of a number of diseases. Here, we report the first successful fabrication and remarkable properties of nanofiber sensors for EPR-oximetry applications.

A versatile LabVIEW and field-programmable gate array-based scanning probe microscope for in operando electronic device characterization.

Understanding the complex properties of electronic and spintronic devices at the micro- and nano-scale is a topic of intense current interest as it becomes increasingly important for scientific progress and technological applications. In operando characterization of such devices by scanning probe techniques is particularly well-suited for the microscopic study of these properties. We have developed a scanning probe microscope (SPM) which is capable of both standard force imaging (atomic, magnetic, electrostatic) and simultaneous electrical transport measurements.

Damping of confined modes in a ferromagnetic thin insulating film: angular momentum transfer across a nanoscale field-defined interface.

We observe a dependence of the damping of a confined mode of precessing ferromagnetic magnetization on the size of the mode. The micron-scale mode is created within an extended, unpatterned yttrium iron garnet film by means of the intense local dipolar field of a micromagnetic tip. We find that the damping of the confined mode scales like the surface-to-volume ratio of the mode, indicating an interfacial damping effect (similar to spin pumping) due to the transfer of angular momentum from the confined mode to the spin sink of ferromagnetic material in the surrounding film.

Antiferromagnonic spin transport from Y3Fe5O12 into NiO.

We observe highly efficient dynamic spin injection from Y3Fe5O12 (YIG) into NiO, an antiferromagnetic (AF) insulator, via strong coupling, and robust spin propagation in NiO up to 100-nm thickness mediated by its AF spin correlations. Strikingly, the insertion of a thin NiO layer between YIG and Pt significantly enhances the spin currents driven into Pt, suggesting exceptionally high spin transfer efficiency at both YIG/NiO and NiO/Pt interfaces. This offers a powerful platform for studying AF spin pumping and AF dynamics as well as for exploration of spin manipulation in tailored structures comprising metallic and insulating ferromagnets, antiferromagnets, and nonmagnetic materials.

The effect of spin transport on spin lifetime in nanoscale systems.

Spintronics use the electron spin as a state variable for information processing and storage. This requires manipulation of spin ensembles for data encoding, and spin transport for information transfer. Because of the central importance of lifetime for understanding and controlling spins, mechanisms that determine this lifetime in bulk systems have been extensively studied.

Histone H3 and H4 N-terminal tails in nucleosome arrays at cellular concentrations probed by magic angle spinning NMR spectroscopy.

Chromatin is a supramolecular assembly of DNA and histone proteins, organized into nucleosome repeat units. The dynamics of chromatin organization regulates DNA accessibility to eukaryotic transcription and DNA repair complexes. Yet, the structural and dynamic properties of chromatin at high concentrations characteristic of the cellular environment (>∼200 mg/mL) are largely unexplored at the molecular level.

Control of magnetocrystalline anisotropy by epitaxial strain in double perovskite Sr(2)FeMoO(6) films.

We demonstrate tuning of magnetocrystalline anisotropy in high-quality Sr(2)FeMoO(6) epitaxial films over a range of several thousand Gauss using strain induced by epitaxial growth on substrates of varying lattice constants. Spectroscopic measurements reveal a striking, linear dependence of the out-of-plane anisotropy on the strain-induced tetragonal distortion of the Sr(2)FeMoO(6) lattice. This anisotropy can be tuned from +2000 to -3300 Oe, a range sufficient to rotate the easy axis from in plane to out of plane.

The role of diffusion in ferritin-induced relaxation enhancement of protons.

The influence of proton diffusion on nuclear magnetic resonance (NMR) relaxation was investigated in the presence of horse spleen ferritin at 7 T. Binary mixtures of water and glycerol were used to control diffusion within the range of 0.6-2.

A strong ferroelectric ferromagnet created by means of spin-lattice coupling.

Ferroelectric ferromagnets are exceedingly rare, fundamentally interesting multiferroic materials that could give rise to new technologies in which the low power and high speed of field-effect electronics are combined with the permanence and routability of voltage-controlled ferromagnetism. Furthermore, the properties of the few compounds that simultaneously exhibit these phenomena are insignificant in comparison with those of useful ferroelectrics or ferromagnets: their spontaneous polarizations or magnetizations are smaller by a factor of 1,000 or more. The same holds for magnetic- or electric-field-induced multiferroics.