A5088739982- Magnetic properties of thin films
- Characterization and Applications of Magnetic Nanoparticles
- Theoretical and Computational Physics
- Magneto-Optical Properties and Applications
- Physics of Superconductivity and Magnetism
- Magnetic Properties and Applications
- Quantum and electron transport phenomena
- Magnetic Bearings and Levitation Dynamics
- Geomagnetism and Paleomagnetism Studies
- Advanced Electron Microscopy Techniques and Applications
- Advanced X-ray Imaging Techniques
- Magnetic confinement fusion research
- Force Microscopy Techniques and Applications
- Electric Motor Design and Analysis
- Magnetic and transport properties of perovskites and related materials
- Vibration Control and Rheological Fluids
- Acoustic Wave Resonator Technologies
- Cold Atom Physics and Bose-Einstein Condensates
- Mechanical and Optical Resonators
- Structural Engineering and Vibration Analysis
- Silicon Nanostructures and Photoluminescence
- Ion-surface interactions and analysis
- Nanowire Synthesis and Applications
- Magnetic Field Sensors Techniques
- Particle accelerators and beam dynamics
Colorado State University
2015-2025
Conference Board
2023-2024
Antea Group (France)
2023-2024
Institute of Electrical and Electronics Engineers
2022-2024
Alpha Omega Electromagnetics (United States)
2023
University of Colorado Colorado Springs
2022
Alfred I. duPont Hospital for Children
2022
Bryn Mawr College
2014-2022
University of Tennessee at Knoxville
2022
University of Delaware
2022
We report a high-resolution experimental detection of the resonant behavior magnetic vortices confined in small disk-shaped ferromagnetic dots. The samples are magnetically soft Fe-Ni disks diameter 1.1 and $2.2\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{m}$ thickness 20 40 nm, patterned via electron-beam lithography onto microwave coplanar waveguides. vortex excitation spectra were probed by vector network analyzer operating reflection mode, which records derivative real imaginary...
Here, we study a magnonic crystal made of low-damping yttrium iron garnet that utilizes pseudo-caustic spin wave beams generated from subwavelength square well features arranged in two-dimensional array. The lattice symmetry and the angle between caustic beam propagation direction applied magnetic field were tailored to optimize interaction waves with engineered defects. A prominent, narrow 3 MHz feature large rejection efficiency is observed transmission spectrum could be useful as...
The spin dynamics are calculated for a model system consisting of magnetically soft, layered nanomagnets, in which two ferromagnetic (F) cylindrical dots, each with magnetic vortex ground state, separated by non-magnetic spacer (N). This permits study the effects interlayer magnetostatic interactions on dynamics. was explored applying equations motion core positions. restoring force taking into account assuming realistic surface charge free distribution. For tri-layer F/N/F dots opposite...
A magnetic vortex confined in a magnetically soft ferromagnet with micron-sized dimensions possesses characteristic dynamic excitation known as translational mode that corresponds to spiral-like precession of the core around its equilibrium position. We report micromagnetic modeling and experimental detection using microwave reflection technique field tunability this $40\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ thick,...
Rapid progress in information technologies has spurred the need for innovative memory concepts, which advanced data-processing methods and tailor-made materials are required. Here we introduce a previously unexplored nanoscale magnetic object: an analog vortex controlled by electric-field-induced ion motion, termed magneto-ionic or "vortion". This state arises from paramagnetic FeCoN through voltage gating gradual N3– extraction within patterned nanodots. Unlike traditional states, vortions...
Submicron, circular, ferromagnetic-antiferromagnetic dots exhibit different magnetization reversal mechanisms depending on the direction of magnetic applied field. Shifted, constricted hysteresis loops, typical for vortex formation, are observed fields along exchange bias direction. However, close to perpendicular direction, occurs via coherent rotation. Magnetic force microscopy imaging together with micromagnetic simulations used further clarify switching behaviors.
The magnetic properties of a trilayer system involving two ferromagnetic disks separated by nonmagnetic spacer differ from those isolated dots due to the magnetostatic and interlayer exchange coupling across spacer. reversal process for this has been investigated experimentally, analytically numerically permalloy $({\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20})$ with thicknesses up $40\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ radii $0.25--1.25\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{m}$ Cu...
A magnetic vortex in a restricted geometry possesses nondegenerate translational excitation that corresponds to circular motion of its core at characteristic frequency. For 40-nm thick, micron-sized permalloy elements, we find the translational-mode microwave absorption peak splits into two peaks differ frequency by up 25% as driving field is increased. An analysis micromagnetic equations shows for large fields stable solutions emerge.
Magnetic skyrmions are topologically protected spin textures that have attracted considerable interest recently. This paper reports the discovery of a topological memory effect, which provides promising new avenue for information encryption and recovery. The authors demonstrate experimentally antiferromagnetically (AFM)-coupled bubble skyrmion pairs stabilized in Co/Gd/Pt multilayered film at room temperature evolve into complex in-plane as is lowered then reform completely when warmed back...
The effect of imprinting symmetric and displaced vortex structures into an antiferromagnetic material is investigated in micron-sized disks consisting exchange coupled ferromagnetic-antiferromagnetic bilayers. imprint vortices manifests itself by the occurrence a new type asymmetric hysteresis loops characterized curved, reversible, central sections with nonzero remanent magnetization. Such achieved cooling through blocking temperature system small fields. Micromagnetic simulations reveal...
We investigate the reversal behavior of circularly exchange-biased micron-sized bilayer disks Permalloy (Py)/IrMn and CoFe/IrMn. A circular exchange bias is induced by imprinting vortex configuration ferromagnetic layer into IrMn when are cooled in zero external field through blocking temperature IrMn. The resulting has a profound effect on magnetization. In Py/IrMn takes place via motion only, controlled bias; it reversible over range small fields maintains single chirality throughout...
Ensembles of iron nanocrystals up to 25 nm in diameter embedded SiO2 were found exhibit an ultrafast magnetic response a transient out-of-plane field. The time varies as function in-plane bias field with the fastest rise times, short 26 ps, observed for both zero and high fields (140 kA/m). Analytical modeling micromagnetic simulations confirm that magnetostatic interactions between nanoparticles play important role dynamic response.
We report a time-resolved imaging and micromagnetic simulation study of the relaxation dynamics magnetic vortex in nonlinear regime. use photoemission electron microscopy calculations to examine emergence patterned ${\text{Ni}}_{80}{\text{Fe}}_{20}$ disks limit long field pulses. show for core shifts beyond $\ensuremath{\sim}20%--25%$ disk radius, initial motion is characterized by distortions vortex, transient cross-tie wall state, instabilities polarization that influence trajectories.
This paper reports on the tuning of both magnetic and electric responses with fields for metglas-Pb (Zr,Ti)O3 based magnetoelectric (ME) heterostructures that can be promising communication sensor applications. The hysteresis loop results indicate a change in in-plane magnetization due to application voltages leads ferromagnetic resonance frequency by up about 210 MHz field. Furthermore, these structures show high ME voltage coefficient detection 2 nT ac field low noise floor.
We demonstrate the first real-space recording of nanoscale dynamic interactions using single-shot soft x-ray (SXR) full-field laser microscopy. A sequence flash images acquired with a table-top SXR was used to capture motion rapidly oscillating magnetic nanoprobe. Changes 30 nm in oscillation amplitude were detected when nanoprobe made interact stray fields from sample. The visualization dynamics real space can significantly contribute understanding processes and accelerate development new...
Integrating patterned, low-loss magnetic materials into microwave devices and circuits presents many challenges due to the specific conditions that are required grow ferrite materials, driving need for flip-chip other indirect fabrication techniques. The ($\alpha = 3.98 \pm 0.22 \times 10^{-5}$), room-temperature ferrimagnetic coordination compound vanadium tetracyanoethylene ($\mathrm{V[TCNE]}_x$) is a promising new material these applications potentially compatible with semiconductor...
Ferromagnetic dots coupled to a thin antiferromagnet reverse<italic>via</italic>a distorted viscous vortex state.
The dynamics of individual magnetic vortices and vortex pairs confined in lithographically defined ferromagnetic ellipses were measured using a microwave reflection technique. Resonance frequencies detected the subgigahertz range for Ni80Fe20 (Permalloy) ranging size from 3 by 1.5μm to 1 0.5μm, 40nm thickness. Micromagnetic simulations indicate that single mode observed one is translational two eigenmodes associated with pair correspond coupled modes parallel or antiparallel core...
We report the polarity reversal of a magnetic vortex core using nonresonant in-plane pulsed field arbitrary waveform studied time-resolved x-ray photoemission electron microscopy and micromagnetic simulations. The imaging simulations show that 5 mT pulse, higher than critical for nonlinear effects, effectively leads to randomization polarity. further onset stochastic does not necessarily coincide with field, leading window predictable reversal.
We find that ensembles of iron nanocrystals embedded within a matrix $\mathrm{Si}{\mathrm{O}}_{2}$ exhibit both large Faraday rotation and ultrafast magnetic relaxation. The Verdet constant is $6.3\ifmmode^\circ\else\textdegree\fi{}\ifmmode\pm\else\textpm\fi{}0.4\ifmmode^\circ\else\textdegree\fi{}∕\mathrm{cm}∕\mathrm{Oe}$ still-unsaturated $3.8\ifmmode^\circ\else\textdegree\fi{}\ifmmode\pm\else\textpm\fi{}0.2\ifmmode^\circ\else\textdegree\fi{}∕\ensuremath{\mu}\mathrm{m}$ was observed at...
The effect of patterning on the shift hysteresis loop HE and coercivity HC in a system composed two perpendicularly exchange-coupled ferromagnets (NiFe sputtered onto [Pt∕Co] multilayer) is investigated long stripes square dots. Setting exchange bias coupling along results threefold increase compared to continuous films. increases dramatically when set perpendicular also Magnetic force microscopy studies micromagnetic simulations suggest that differences number orientation magnetic domains...