A5014187476- Magnetic properties of thin films
- Quantum and electron transport phenomena
- Physics of Superconductivity and Magnetism
- Advanced Condensed Matter Physics
- Theoretical and Computational Physics
- Characterization and Applications of Magnetic Nanoparticles
- Advanced Memory and Neural Computing
- Magneto-Optical Properties and Applications
- Multiferroics and related materials
- Quantum many-body systems
- Magnetic Properties and Applications
- Nonlinear Dynamics and Pattern Formation
- Advanced X-ray Imaging Techniques
- Topological Materials and Phenomena
- Mechanical and Optical Resonators
- Neural Networks and Reservoir Computing
- Ferroelectric and Negative Capacitance Devices
- Atomic and Subatomic Physics Research
- Magnetic and transport properties of perovskites and related materials
- Crystallography and Radiation Phenomena
- Semiconductor Quantum Structures and Devices
- Phase-change materials and chalcogenides
- Magnetic confinement fusion research
- Cold Atom Physics and Bose-Einstein Condensates
- X-ray Spectroscopy and Fluorescence Analysis
University of Colorado Colorado Springs
2021-2025
Northumbria University
2020-2023
University of Colorado System
2023
Université Paris-Saclay
2022
University of Colorado Boulder
2016-2022
Laboratoire Albert Fert
2022
Centre National de la Recherche Scientifique
2022
University of Gothenburg
2011-2018
Chalmers University of Technology
2015-2018
Nanosc (Sweden)
2014-2015
Magnonics addresses the physical properties of spin waves and utilizes them for data processing. Scalability down to atomic dimensions, operation in GHz-to-THz frequency range, utilization nonlinear nonreciprocal phenomena, compatibility with CMOS are just a few many advantages offered by magnons. Although magnonics is still primarily positioned academic domain, scientific technological challenges field being extensively investigated, proof-of-concept prototypes have already been realized...
Dissipative solitons have been reported in a wide range of nonlinear systems, but the observation their magnetic analog has experimentally challenging. Using spin transfer torque underneath nanocontact on thin film with perpendicular anisotropy (PMA), we observed generation dissipative droplet and report rich dynamical properties. Micromagnetic simulations identify automodulation frequencies, including oscillatory motion, "spinning," "breather" states. The can be controlled by using both...
Magnetic skyrmions are topologically non-trivial spin textures that manifest themselves as quasiparticles in ferromagnetic thin films or noncentrosymmetric bulk materials. So far attention has focused on stabilized either by the Dzyaloshinskii–Moriya interaction (DMI) dipolar interaction, where latter case excitations known bubble skyrmions. Here we demonstrate existence of a dynamically skyrmion, which exists even when interactions and DMI absent. We establish how such dynamic can be...
It has been argued that if multiple spin wave modes are competing for the same centrally located energy source, as in a nanocontact torque oscillator, only one mode should survive steady state. Here, experimental conditions necessary coexistence explored. Mode is facilitated by local field asymmetries induced spatially inhomogeneous Oersted field, which leads to physical separation of modes, and further promoted localization at reduced applied angles. Finally, both simulation experiment...
Magnetization dynamics in an artificial square spin-ice lattice made of ${\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20}$ with magnetic field applied the plane is investigated by broadband ferromagnetic resonance spectroscopy. The experimentally observed dispersion shows a rich spectrum modes corresponding to different magnetization states. These states are determined exchange and dipolar interaction between individual islands, as confirmed semianalytical model. In low regime below 400 Oe hysteretic...
Over the past few years, study of magnetization dynamics in artificial spin ices has become a vibrant field study. Artificial are ensembles geometrically arranged, interacting magnetic nanoislands, which display frustration by design. These were initially created to mimic behavior rare earth pyrochlore materials and emergent using two-dimensional measurement techniques. Recently, it clear that is possible create ices, can potentially be used as functional materials. In this perspective, we...
Abstract Strongly-interacting nanomagnetic arrays are ideal systems for exploring reconfigurable magnonics. They provide huge microstate spaces and integrated solutions storage neuromorphic computing alongside GHz functionality. These may be broadly assessed by their range of reliably accessible states the strength magnon coupling phenomena nonlinearities. Increasingly, expanding into three-dimensional architectures. This has enhanced available magnetic microstates functional behaviours, but...
We demonstrate magnetization auto-oscillations driven by pure spin currents in Hall nano-oscillators based on CoFeB/Pt bilayers. Despite the very low anisotropic magnetoresistance of CoFeB, a substantial microwave signal power can be detected, even at room temperature, indicating that sizable wave amplitude is generated. Spin torque ferromagnetic resonance measurements reveal generated auto-oscillation frequency lies below CoFeB and therefore well described self-localized bullet mode.
Artificial square ices are structures composed of magnetic nanoelements arranged on the sites a two-dimensional lattice, such that there four interacting elements at each vertex, leading to geometrical frustration. Using semianalytical approach, we show exhibit rich spin-wave band structure is tunable both by external fields and magnetization configuration individual elements. Internal degrees freedom can give rise equilibrium states with bent element edges characteristic excitations; in...
Sub-picosecond magnetisation manipulation via femtosecond optical pumping has attracted wide attention ever since its original discovery in 1996. However, the spatial evolution of is not yet well understood, part due to difficulty experimentally probing such rapid dynamics. Here, we find evidence a universal magnetic order recovery ferrimagnets with perpendicular anisotropy nonlinear magnon processes. We identify localisation and coalescence processes, whereby localised textures nucleate...
Artificial spin ices are ensembles of geometrically-arranged, interacting nanomagnets which have shown promising potential for the realization reconfigurable magnonic crystals. Such systems allow manipulation waves on nanoscale and their use as information carriers. However, there presently two general obstacles to artificial ice-based crystals: magnetic state is difficult reconfigure magnetostatic interactions between nanoislands often weak, preventing mode coupling. We demonstrate, using...
Magnons, the quantum-mechanical fundamental excitations of magnetic solids, are bosons whose number does not need to be conserved in scattering processes. Microwave-induced parametric magnon processes, often called Suhl instabilities, have been believed occur thin films only, where quasi-continuous bands exist. Here, we reveal existence such nonlinear magnon-magnon processes and their coherence ensembles nanostructures known as artificial spin ice. We find that these systems exhibit...
Magnetic dissipative droplets are localized, strongly nonlinear dynamical modes excited in nanocontact spin valves with perpendicular magnetic anisotropy. These find potential application nanoscale structures for storage and computation, but droplet studies have so far been limited to extended thin films. Here, numerical asymptotic analyses used demonstrate the existence properties of novel solitons confined structures. As a nanowire's width is decreased fixed size at its center, observed...
Abstract Static and dynamic magnetic solitons play a critical role in applied nanomagnetism. Magnetic droplets, type of non-topological dissipative soliton, can be nucleated sustained nanocontact spin-torque oscillators with perpendicular anisotropy free layers. Here, we perform detailed experimental determination the full droplet nucleation boundary current–field plane for wide range sizes demonstrate its excellent agreement an analytical expression originating from stability analysis. Our...
We present recent experimental and numerical advancements in the understanding of spin transfer torque generated magnetic droplet solitons. The work focuses on nano-contact oscillators (NC-STOs) based orthogonal (pseudo) valves where Co fixed layer has an easy-plane anisotropy, [Co/Ni] free a strong perpendicular anisotropy. NC-STO resistance microwave signal generation are measured simultaneously as function drive current applied field. Both exhibit dramatic transitions at certain dependent...
Microwave magnetodynamics in ferromagnets are often studied the small-amplitude or weakly nonlinear regime corresponding to modulations of a well-defined magnetic state. However, strongly regimes, where aforementioned approximations not applicable, have become experimentally accessible. By re-interpreting governing Landau-Lifshitz equation motion, we derive an exact set equations dispersive hydrodynamic form that amenable analytical study even when full nonlinearity and exchange dispersion...
Magnetic nanoparticles such as FePt in the L1 0 phase are bedrock of our current data storage technology. As grains become smaller to keep up with technological demands, superparamagnetic limit calls for materials higher magnetocrystalline anisotropy. This, turn, reduces magnetic exchange length just a few nanometers, enabling structures be induced within nanoparticles. Here, we describe existence spin-wave solitons, dynamic localized bound states excitations, We show time-resolved x-ray...
We demonstrate that the transient non-autonomous dynamics of a spin torque nano-oscillator (STNO) under radio-frequency (rf) driving signal is qualitatively different from described by Adler model. If external rf current $I_{rf}$ larger than certain critical value $I_{cr}$ (determined STNO bias and damping) strong oscillations power phase develop in regime. The frequency these increases with as $\propto\sqrt{I_{rf} - I_{cr}}$ can reach several GHz, whereas damping rate almost independent...
The current controlled modulation of nano-contact based spin torque oscillator (STO) pairs is studied in both the synchronized and non-synchronized states. state shows a well behaved demonstrates robust mutual locking even under strong modulation. power distribution sidebands can be quantitatively described by assuming single model. However, state, are not model, indicating interactions between two individual STOs. These findings promising for potential applications requiring large STO arrays.
We present a comprehensive review of the most recent advances in nano-contact spin torque oscillators (NC-STOs).NC-STOs are highly tunable, with both applied magnetic field and dc current, broadband microwave signal generators.As opposed to nano-pillar geometry, where lateral cross section entire device has been confined typically <100 nm diameter, NC-STOs it is only current injection site that laterally on top an extended film stack.Three distinct material combinations will be discussed:...