A5031714465- Advanced Condensed Matter Physics
- Theoretical and Computational Physics
- Physics of Superconductivity and Magnetism
- Magnetic and transport properties of perovskites and related materials
- Quantum many-body systems
- Magnetic properties of thin films
- Multiferroics and related materials
- High Entropy Alloys Studies
- Electronic and Structural Properties of Oxides
- Topological Materials and Phenomena
- Ferroelectric and Piezoelectric Materials
- Underwater Acoustics Research
- Quantum and Classical Electrodynamics
- Liquid Crystal Research Advancements
- Microfluidic and Bio-sensing Technologies
- Particle Accelerators and Free-Electron Lasers
- Geophysics and Sensor Technology
- High-Temperature Coating Behaviors
- Magnesium Alloys: Properties and Applications
- Aerodynamics and Acoustics in Jet Flows
- Dynamics and Control of Mechanical Systems
- Lattice Boltzmann Simulation Studies
- Rare-earth and actinide compounds
- Quantum chaos and dynamical systems
- ZnO doping and properties
Baylor University
2023-2025
Aalto University
2019-2023
Paul Scherrer Institute
2012-2022
Lawrence Berkeley National Laboratory
2016-2020
ETH Zurich
2013-2017
TU Wien
2010
We study the thermal relaxation of artificial spin ice with photoemission electron microscopy, and are able to directly observe how such a system finds its way from an energetically excited state ground state. On plotting vertex-type populations as function time, we can characterize relaxation, which occurs in two stages, namely string domain regime. Kinetic Monte Carlo simulations agree well temporal evolution magnetic when including disorder, experimental results be explained by...
Magnetic monopoles, proposed as elementary particles that act isolated magnetic south and north poles, have long attracted research interest analogs to electric charge. In solid-state physics, a classical analog these elusive has emerged topological excitations within pyrochlore spin ice systems. We present the first real-time imaging of emergent monopole motion in macroscopically degenerate artificial system consisting thermally activated Ising-type nanomagnets lithographically arranged...
Abstract Magnetoelectric coupling at room temperature in multiferroic materials, such as BiFeO 3 , is one of the leading candidates to develop low-power spintronics and emerging memory technologies. Although extensive research activity has been devoted recently exploring physical properties, especially focusing on ferroelectricity antiferromagnetism chemically modified a concrete understanding magnetoelectric yet be fulfilled. We have discovered that La substitutions Bi-site lead progressive...
We present a direct magnetic imaging study on the thermal macrospin ordering of artificial kagome spin ice building blocks. Using photoemission electron microscopy, employing x-ray circular dichroism, we are able to resolve single domain nature macrospins and determine states combined block structures. The nano-patterning material selection allows thermally activated magnetization reversal for occur. is dominated by ground state, consistent with state ordering. This work paves way...
Abstract Electric-field control of magnetism requires deterministic the magnetic order and understanding magnetoelectric coupling in multiferroics like BiFeO 3 EuTiO . Despite this critical need, there are few studies on strain evolution films. Here, (110)-oriented films, we reveal that while polarization structure remains relatively unaffected, can continuously tune orientation antiferromagnetic-spin axis across a wide angular space, resulting an unexpected deviation classical perpendicular...
Abstract Electric charge screening is a fundamental principle governing the behaviour in variety of systems nature. Through reconfiguration local environment, Coulomb attraction between electric charges decreased, leading, for example, to creation polaron states solids or hydration shells around proteins water. Here, we directly visualize real-time and decay screened magnetic configurations two-dimensional artificial spin ice system, dipolar dice lattice. By comparing temperature dependent...
We present a study on the structural and magnetic properties of thin films high entropy perovskite $\mathrm{Dy}({\mathrm{Fe}}_{0.2}{\mathrm{Mn}}_{0.2}{\mathrm{Co}}_{0.2}{\mathrm{Cr}}_{0.2}{\mathrm{Ni}}_{0.2}){\mathrm{O}}_{3}$ (Dy5BO). An element-sensitive investigation was performed using synchrotron-based x-ray absorption spectroscopy, employing circular linear dichroism. The results reveal that moments residing $3d$ transition metal ions rare-earth $\mathrm{Dy}$ produce saturation...
In Refs. [1-4] Dirac and Schwinger showed the existence of a magnetic monopole required charge quantization condition which we write following as $\frac{eg}{4\pi\hbar}=\frac{n}{2},\; n=0,\pm 1,\; \pm 2, \ldots$. Here, $g$ is $e$ electric positron. Recently, in [5,6], it has been shown experimentally that frustrated spin-ice systems exhibit 'emergent' monopoles. We show that, within experimental errors, respective charges obey Dirac-Schwinger condition. Possible implications are discussed.
We introduce the Aleppo spin ice geometry, another variation of decimated square patterns, which in contrast to similar systems previously studied, does not exhibit vertex frustration. Using synchrotron-based photoemission electron microscopy, we directly visualize low-energy states achieved after thermal annealing, addition temperature-dependent moment fluctuations. The results reveal observation ground state patterns and absence ergodicity-breaking dynamics. Our observations further...
High-entropy oxide thin films have recently been introduced as an attractive strategy to design and enhance ferroic properties. Here, the authors perform element-sensitive x-ray absorption spectroscopy magnetometry on high-entropy perovskite films, shedding light how different transition metal elements contribute overall magnetic response. The results demonstrate not only disorder can lead enhancement of properties but also provide a route towards further improvements other desired in...
Spin ice materials represent an intriguing class of frustrated magnetic systems which, through their geometry, admit exponential number approximately degenerate configurations. In this paper, the relaxation properties a thermally active artificial kagome spin system are studied. Through application external field, out-of-equilibrium vertex charge ordered configuration is selected and relaxed under approximate zero-field conditions. Using x-ray photo-emission electron microscopy, moment...
We have performed a study of thermally driven magnetic relaxation in building blocks artificial kagome spin ice. For room-temperature measurements, we observe that low-energy states are accessed with high efficiency, particularly structures strong dipolar coupling and low thicknesses. With carefully tuned heating experiments, demonstrate how active ice systems relax magnetically from higher-energy eventually fall into states. The methods applied our work offer the possibility to...
Abstract Geometrical frustration occurs when entities in a system, subject to given lattice constraints, are hindered simultaneously minimize their local interactions. In magnetism, systems incorporating geometrical fascinating, as behavior is not only hard predict, but also leads the emergence of exotic states matter. Here, we provide first look into an artificial frustrated dipolar trident lattice, where balance competing interactions between nearest-neighbor magnetic moments can be...
We explore the thermodynamics in two-dimensional arrays consisting of Ising-type nanomagnets lithographically arranged onto random sites and angular orientations. Introducing these basic spin-glass ingredients, we study characteristic features low-energy states achieved, following thermal-annealing protocols. From direct visualization real-time dynamics, record relaxation timescales together with magnetic susceptibility variations over temperature, revealing trends towards short-range order...
We image the remnant magnetization configurations of CoFeB and permalloy nanotubes (NTs) using x-ray magnetic circular dichroism photo-emission electron microscopy. The images provide direct evidence for flux-closure configurations, including a global vortex state, in which points circumferentially around NT axis. Furthermore, micromagnetic simulations predict measurements confirm that states can be programmed as equilibrium by reducing aspect ratio.
High-resolution kagome lattice structures with feature sizes down to the sub-50 nm regime are fabricated using diffraction-based extreme ultraviolet interference lithography. The resulting pattern of multiple beams is sensitive relative phase interfering beams. precise control their phases achieved by positioning transmission diffraction gratings on a mask high-end electron beam lithography tool. presented method may find applications in providing high-resolution and large-area for studies...
Ever since its introduction by Ludwig Boltzmann, the ergodic hypothesis became a cornerstone analytical concept of equilibrium thermodynamics and complex dynamic processes. Examples relevance range from modeling decision-making processes in brain science to economic predictions. In condensed matter physics, ergodicity remains largely investigated via theoretical computational models. Here, we demonstrate direct real-space observation transitions vertex-frustrated artificial spin ice. Using...
We present a study on the structural and magnetic properties of Sr(Fe0.2Mn0.2Co0.2Ti0.2V0.2)O3 (S5BO) high-entropy oxide perovskite thin films. use synchrotron-based x-ray absorption spectroscopy employing circular dichroism (XMCD) reveal an enhanced presence high-spin Co2+, which appears to feature response opposing that two other transition metal elements, Fe Mn. This is marked by both opposite XMCD signals inverted hysteresis loop for Co, while Mn show regularly shaped curves, as picture...
We have studied low-energy configurations in two-dimensional arrays consisting of Ising-type dipolar coupled nanomagnets lithographically defined onto a Cairo lattice, thus dubbed the lattice. Employing synchrotron-based photoemission electron microscopy (PEEM), we perform real-space imaging moment achieved after thermal annealing. These states are then characterized terms vertex populations, spin- and emergent magnetic charge correlations, topology-enforced ice rule. The results reveal...