A5081293348- Magnetic properties of thin films
- Advanced Electron Microscopy Techniques and Applications
- Electron and X-Ray Spectroscopy Techniques
- Theoretical and Computational Physics
- Magnetic and transport properties of perovskites and related materials
- Magnetic Properties and Applications
- Physics of Superconductivity and Magnetism
- Ion-surface interactions and analysis
- ZnO doping and properties
- Advanced Materials Characterization Techniques
- Multiferroics and related materials
- Electronic and Structural Properties of Oxides
- Integrated Circuits and Semiconductor Failure Analysis
- Particle Detector Development and Performance
- GaN-based semiconductor devices and materials
- Metal and Thin Film Mechanics
- Ga2O3 and related materials
- Quantum and electron transport phenomena
- Advanced X-ray Imaging Techniques
- Near-Field Optical Microscopy
- Advanced Surface Polishing Techniques
- Advanced Memory and Neural Computing
- Ferroelectric and Piezoelectric Materials
- Characterization and Applications of Magnetic Nanoparticles
- Metallic Glasses and Amorphous Alloys
University of Glasgow
2014-2024
JEOL (United Kingdom)
2024
Scottish Universities Physics Alliance
2015-2021
University of Leeds
2021
UNSW Sydney
2005-2010
Materials Science & Engineering
2006
We investigate the Dzyaloshinskii-Moriya interactions (DMIs) in perpendicularly magnetized thin films of Pt/Co/Pt and Pt/Co/Ir/Pt. To study effective DMI, arising at either side ferromagnet, we use a field-driven domain wall creep-based method. The only magnetic field removes possibility mixing with current-related effects such as spin Hall effect or Rashba field, well complexity from lithographic patterning. Inserting an ultrathin layer Ir top Co/Pt interface allows us to access DMI...
Light-electron interaction in empty space is the seminal ingredient for free-electron lasers and also controlling electron beams to dynamically investigate materials molecules. Pushing coherent control of free electrons by light unexplored timescales, below attosecond, would enable unprecedented applications light-assisted quantum circuits diagnostics at extremely small such as those governing intramolecular electronic motion nuclear phenomena. We experimentally demonstrate attosecond...
We demonstrate that light-induced heat pulses of different duration and energy can write skyrmions in a broad range temperatures magnetic field FeGe. Using combination camera-rate pump-probe cryo-Lorentz Transmission Electron Microscopy, we directly resolve the spatio-temporal evolution magnetization ensuing optical excitation. The skyrmion lattice was found to maintain its structural properties during laser-induced demagnetization, recovery initial state happened sub-{\mu}s {\mu}s range,...
We report on domain wall pinning behavior and the potential-energy landscapes created by notches of two different geometries in planar Permalloy nanowires. Domain depinning was probed experimentally using spatially resolved magneto-optical Kerr effect measurements. The spin structure pinned walls determined Lorentz microscopy, also analyzed micromagnetic simulations, which are good qualitative agreement with experimental results. All notch structures have dimensions that comparable length...
Abstract The microscopic magnetization variation in magnetic domain walls thin films is a crucial property when considering the torques driving their dynamic behaviour. For possessing out-of-plane anisotropy normally presence of Néel not favoured due to magnetostatic considerations. However, they have right structure respond exerted by spin Hall effect. Their existence an indicator interfacial Dzyaloshinskii–Moriya interaction (DMI). Here we present direct imaging with fixed chirality...
The application of differential phase contrast imaging to the study polycrystalline magnetic thin films and nanostructures has been hampered by strong diffraction resulting from granular structure materials. In this paper we demonstrate how a pixelated detector used detect bright field disk in aberration corrected scanning transmission electron microscopy (STEM) subsequent processing acquired data allows efficient enhancement images. Initial results charged coupled device (CCD) camera highly...
Theoretical analysis and Lorentz transmission electron microscopy (LTEM) investigations in an FeGe wedge demonstrate that chiral twists arising near the surfaces of noncentrosymmetric ferromagnets [Meynell et al., Phys. Rev. B 90, 014406 (2014)] provide a stabilization mechanism for magnetic Skyrmion lattices helicoids cubic helimagnet nanolayers. The phase diagram obtained freestanding nanolayers shows magnetization processes differ fundamentally from those bulk helimagnets are...
Understanding the conditions determining appearance of stable chiral spin topological excitations is a central problem in condensed matter physics and related fields. This work provides first unambiguous demonstration discretization due to macroscopic phase coherence metastability for excitations, evidence mechanisms underlying its appearance. was achieved through use an advanced Lorentz electron microscope with highest possible resolution imaging textures. The results provide new insights...
Continued development of GaN-based light emitting diodes is being hampered by constraints imposed current non-native substrates. ZnO a promising alternative substrate but it decomposes under the conditions used in conventional GaN metal organic vapor phase epitaxy (MOVPE). In this work, was grown on ZnO∕c-Al2O3 using low temperature/pressure MOVPE with N2 as carrier and dimethylhydrazine N source. Characterization confirmed epitaxial growth GaN. The lifted-off c-Al2O3 chemically etching away...
In this paper we report quantitative measurements of the imaging performance for current generation hybrid pixel detector, Medipix3, used as a direct electron detector. We have measured modulation transfer function and detective quantum efficiency at beam energies 60 80keV. single mode, energy threshold values can be chosen to maximize either or efficiency, obtaining near to, exceeding those theoretical detector with square pixels. The Medipix3 charge summing mode delivers simultaneous, high...
Capturing and controlling plasmons at buried interfaces with nanometre femtosecond resolution has yet to be achieved is critical for next generation plasmonic devices. Here we use light excite interference patterns a metal-dielectric interface in nanostructured thin film. Plasmons are launched from photoexcited array of nanocavities their propagation followed via photon-induced near-field electron microscopy (PINEM). The resulting movie directly captures the plasmon dynamics, allowing...
Magnetic skyrmions are promising candidates as information carriers in logic or storage devices thanks to their robustness, guaranteed by the topological protection, and nanometric size. Currently, little is known about influence of parameters such disorder, defects external stimuli, on long-range spatial distribution temporal evolution skyrmion lattice. Here, using a large (7.3x7.3{\mu}m$^{2}$) single crystal nano-slice Cu$_{2}$OSeO$_{3}$, we image up 70,000 skyrmions, means cryo-Lorentz...
The quantum interference between ultrafast light and electron pulses enables the holographic reconstruction of nanoscale fields.
Differential phase contrast (DPC) imaging in the scanning transmission electron microscope is applied to study of a charged antiphase domain boundary doped bismuth ferrite. A clear differential signal seen, which matches expected direction electric field at boundary. However, further by scanned diffraction reveals that there no measurable deflection primary disc and hence significant free E-field material. Instead, DPC arises from modulation intensity profile within vicinity Simulations are...
We have utilised a high spatial resolution imaging method, Differential Phase Contrast (DPC) performed in scanning transmission electron microscope (STEM), for precise measurement of the magnetic induction distribution skyrmion states noncentrosymmetric magnetically ordered materials. Applied to investigate internal structure hexagonal lattice cells, stabilised by an out-plane applied field FeGe nanowedge specimen, mapping in-plane component has yielded "average" profiles and observation...
Skyrmions in ultrathin ferromagnetic metal (FM)/heavy (HM) multilayer systems produced by conventional sputtering methods have recently generated huge interest due to their applications the field of spintronics. The sandwich structure with two correctly-chosen heavy layers provides an additive interfacial exchange interaction which promotes domain wall or skyrmion spin textures that are Néel character and a fixed chirality. Lorentz transmission electron microscopy (TEM) is high resolution...
Abstract A latex technique is used to prepare graphene/polystyrene and graphene/poly(propylene) composites with varying GR loadings. Their electrical properties the corresponding volume organisation of networks are studied. Percolation thresholds for conduction found be about 0.9 0.4 wt% GR/PS GR/PP maximum obtained conductivities 12 S m −1 loadings 2 wt%, respectively. Investigations using SEM conductivity measurements show that preparation conditions forms an isotropic 3D network in PS...
Nanoscale modifications of strain and magnetic anisotropy can open pathways to engineering domains for device applications. A periodic domain structure be stabilized in sub-200 nm wide linear as well curved magnets, embedded within a flat non-ferromagnetic thin film. The nanomagnets are produced B2-ordered Fe60 Al40 film, where local irradiation by focused ion beam causes the formation disordered strongly ferromagnetic regions A2 . An anisotropic lattice relaxation is observed, such that...
Magnetic skyrmions are particle-like deformations in a magnetic texture. They have great potential as information carriers spintronic devices because of their interesting topological properties and favorable motion under spin currents. A new method nucleating at nanoscale defect sites, created controlled manner with focused ion beam irradiation, polycrystalline multilayer samples an interfacial Dzyaloshinskii-Moriya interaction, is reported. This has three notable advantages: 1) localization...
Abstract Traditional image acquisition for cryo focused ion-beam scanning electron microscopy (FIB-SEM) tomography often sees thousands of images being captured over a period many hours, with immense data sets produced. When imaging beam sensitive materials, these are compromised by additional constraints related to damage and the devitrification material during imaging, which renders both costly unreliable. Subsampling inpainting proposed as solutions aspects, allowing fast low-dose take...
In synthetic antiferromagnets (SAFs), antiferromagnetic (AFM) order and synthesis using conventional sputtering techniques is combined to produce systems that are advantageous for spintronics applications. Here we present the preparation study of SAF multilayers possessing both perpendicular magnetic anisotropy Dzyaloshinskii-Moriya interaction. The have an antiferromagnetically aligned ground state but can be forced into a full ferromagnetic (FM) alignment by applying out-of-plane field...
Highly aligned conducting polymer nanowires have been grown between two nanometer-scale metal electrodes, providing a simple way to incorporate single and multiple into pre-patterned electrical circuits. A highly sensitive nanowire chemical sensor has fabricated as proof-of-concept of this method we report results concerning the exposure ammonia gas.