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Antiferromagnetic hysteresis above the spin-flop field

Physical Review B 2023年第6期107卷 L060403-L060403页

作者： M. J. Grzybowski C. F. Schippers O. Gomonay K. Rubi M. E. Bal U. Zeitler A. Kozioł-Rachwał M. Szpytma W. Janus B. Kurowska S. Kret M. Gryglas-Borysiewicz B. Koopmans H. J. M. Swagten Department of Applied Physics Eindhoven University of Technology PO Box 513 5600 MB Eindhoven The Netherlands Faculty of Physics University of Warsaw ul. Pasteura 5 PL-02-093 Warsaw Poland Institute of Physics Johannes Gutenberg-University Mainz 55128 Mainz Germany High Field Magnet Laboratory (HFML-EMFL) Radboud University 6525 ED Nijmegen The Netherlands Faculty of Physics and Applied Computer Science AGH University of Science and Technology 30-059 Kraków Poland Institute of Physics Polish Academy of Sciences Al. Lotników 32/46 PL-02-668 Warsaw Poland

Magnetocrystalline anisotropy is essential in the physics of antiferromagnets and commonly treated as a constant, not depending on an external magnetic field. However, we demonstrate that in CoO the anisotropy should necessarily depend on the magnetic field, which is shown by the spin Hall magnetoresistance of the CoO|Pt device. Below the Néel temperature CoO reveals a spin-flop transition at 240 K at 7.0 T, above which a hysteresis in the angular dependence of magnetoresistance unexpectedly persists up to 30 T. This behavior is shown to agree with the presence of the unquenched orbital momentum, which can play an important role in antiferromagnetic spintronics.

关键词： Antiferromagnetism Spin Hall magnetoresistance Spin-orbit coupling Spintronics Antiferromagnets Thin films Transition metal oxides Angular momentum Resistivity measurements Transport techniques

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Antiferromagnetic domains distribution carried by stoichiometry

Antiferromagnetic domains distribution carried by stoichiome...

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2023 IEEE International Magnetic Conference - Short Papers, INTERMAG Short Papers 2023

作者： Mandziak, Anna De La Figuera, Juan Emilio Prieto, Jose Quesada, Adrian Miralles, Cecilia Granados Berja, Alba Aballe, Lucia Foerster, Michael Nino, Miguel Angel Nita, Pawel Solaris Synchrotron Czerwone Maki 98 Cracow30-392 Poland MadridE-28006 Spain MadridE-28049 Spain Alba Synchrotron Light Facility Cells BarcelonaE-08290 Spain Jagiellonian University Faculty of Physics Astronomy and Applied Computer Science ul. prof. Stanislawa Lojasiewicza 11 Cracow30-348 Poland

ISBN: (纸本)9798350338362

We present a spatially resolved X-ray magnetic linear dichroism study of high quality micron-sized mixed nickel-cobalt oxide (NCO) crystals. NixCo1-xO were prepared in-situ by high-temperature oxygen-assisted molecular beam epitaxy on Ru(0001) single crystal. To check the effect of incorporating Ni in the cobalt oxide films, three different composition were prepared. The element specific XMLD measurements reveal strong antiferromagnetic contrast at room temperature and magnetic domains up to one micron wide, reflecting the high structural quality of the islands. By means of vectorial magnetometry, the spin axis orientation of the domains was determined with nanometer spatial resolution, and found to depend on the stoichiometry of prepared crystals. © 2023 IEEE.

关键词： Nickel oxide

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Thermal properties of structurally balanced systems on classical random graphs

arXiv

引用

arXiv 2022年

作者： Malarz, Krzysztof Woloszyn, Maciej AGH University Faculty of Physics and Applied Computer Science al. Mickiewicza 30 Kraków30-059 Poland

The dynamics of social relations and the possibility of reaching the state of structural balance (Heider balance) under the influence of the temperature modeling the social noise level are discussed for interacting actors occupying nodes of classical random graphs. Depending on the graph density D, either a smooth cross-over or a first-order phase transition from a balanced to an imbalanced state of the system is observed with an increase in the thermal noise level. The minimal graph density Dmin for which the first-order phase transition can be observed decreases with the system size N as Dmin ∝ N−0.58(1). For graph densities D > Dmin the reduced critical temperature Tc✶ = Tc/Tc(D = 1) increases with the graph density as Tc✶ ∝ D1.719(6) independently of the system size N. © 2022, CC BY.

关键词： Graph theory

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Constraining the Gravitational Wave Speed in the Early Universe via Gravitational Cherenkov Radiation

arXiv

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arXiv 2025年

作者： Delgado, Paola C.M. Ganz, Alexander Lin, Chunshan Thériault, Roxane CEICO FZU - Institute of Physics of the Czech Academy of Sciences Na Slovance 1999/2 Prague182 00 Czech Republic Institute for Theoretical Physics Leibniz University Hannover Appelstraße 2 Hannover30167 Germany Faculty of Physics Astronomy and Applied Computer Science Jagiellonian University Krakow30-348 Poland

Scalar particles traveling faster than a subluminal gravitational wave generate gravitons via gravitational Cherenkov radiation. In this paper, we investigate graviton production by the primordial plasma within the framework of modified gravity in the early Universe, generating a relic graviton background. We find that for the minimal model, where only the speed of gravitational waves is modified and a standard model plasma minimally couples to gravity, the relic graviton background can be enhanced by several orders of magnitude, but still agrees with the Big Bang Nucleosynthesis (BBN) bound in most cases. Moreover, we also find that for Horndeski theories, such as Galileon theory, the relic background produced by the thermalized scalar field can reach significant amplitudes, exceeding the BBN bound for a region of the parameter space. By requiring the relic graviton background to remain consistent with the BBN constraint, we derive limits on the gravitational wave speed at early times in these modified gravity theories. Copyright © 2025, The Authors. All rights reserved.

关键词： Gravitational effects

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Exploring Environmentally Friendly Corrosion Inhibitors: Insights from Natural and Biomass Residue-Derived Compounds

SSRN

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SSRN 2024年

作者： Othman, Norinsan Kamil Mohammed, Naba Jasim Yusop, Muhammed Rahimi Al-Gburi, Ahmed Jamal Abdullah Materials Science Program Department of Applied Physics Faculty of Science and Technology University Kebangsaan Malaysia Selangor Bangi43600 Malaysia Faculty of Science and Technology School of Chemical Sciences and Food Technology University Kepangsaan Malaysia Selangor Bangi43600 Malaysia Faculty of Electronics and Computer Engineering Universiti Teknikal Malaysia Melaka Hang Tuah Jaya Melaka Durian Tunggal76100 Malaysia

In this investigation, we explored the corrosive effects of date palm seed extracted from natural sources and biomass residues on mild steel in a solution of 0.5 M hydrochloric acid (HCl), employing a combination of experimental and theoretical approaches. Our objective was to scrutinize the interaction of the inhibitor with the metal surface, analyze experimental data, and elucidate how the structural characteristics of the inhibitors influence the corrosion process. The experimental results indicated that as the immersion time and temperature increased, the inhibitory effectiveness declined. Notably, the highest level of inhibition occurred when the concentration of date palm seed extract (DPSE) reached 1100 ppm, showcasing peak inhibitory effects of 95.8% and 97.8% through potentiodynamic polarization and electrochemical impedance spectroscopy techniques, respectively. Additionally, an analysis using X-ray diffraction (XRD) was conducted to scrutinize the chemical composition of the mild steel's surface. The adsorption data were evaluated using adsorption isotherms, revealing that DPSE adhered to the Langmuir adsorption isotherm on the mild steel surface. The Langmuir model exhibited the highest linear regression coefficient value and a slope close to unity. The Gibbs free energy () values suggested that the protection afforded by DPSE involved physical and spontaneous absorption. Examination of the results pertaining to the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) indicated that the carboxyl (COOH) group and the C=C bond were the principal regions exhibiting elevated electron acceptance activity. These components were found to be crucial in the adsorption process on the surface of iron (Fe). © 2024, The Authors. All rights reserved.

关键词： Electrochemical impedance spectroscopy

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Simulating first-order phase transition with hierarchical autoregressive networks

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Physical Review E 2023年第5期107卷 054127-054127页

作者： Piotr Białas Paulina Czarnota Piotr Korcyl Tomasz Stebel Institute of Applied Computer Science Jagiellonian University 30-348 Kraków Poland Faculty of Biochemistry Biophysics and Biotechnology Jagiellonian University 30-387 Kraków Poland Institute of Theoretical Physics Jagiellonian University 30-348 Kraków Poland

We apply the hierarchical autoregressive neural network sampling algorithm to the two-dimensional Q-state Potts model and perform simulations around the phase transition at Q=12. We quantify the performance of the approach in the vicinity of the first-order phase transition and compare it with that of the Wolff cluster algorithm. We find a significant improvement as far as the statistical uncertainty is concerned at a similar numerical effort. In order to efficiently train large neural networks we introduce the technique of pretraining. It allows us to train some neural networks using smaller system sizes and then employ them as starting configurations for larger system sizes. This is possible due to the recursive construction of our hierarchical approach. Our results serve as a demonstration of the performance of the hierarchical approach for systems exhibiting bimodal distributions. Additionally, we provide estimates of the free energy and entropy in the vicinity of the phase transition with statistical uncertainties of the order of 10−7 for the former and 10−3 for the latter based on a statistics of 106 configurations.

关键词： Approximation methods for many-body systems Deep learning Lattice field theory Metropolis algorithm Monte Carlo methods Spin lattice models

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Robust Feature Engineering Techniques for Designing Motor Imagery-Based Bci Systems

SSRN

引用

SSRN 2025年

作者： Gardezi Ahmed, Syed Saim Khan, Mahnoor Bukhari, Syeda Muneeba Khan, Rizwan Ahmed Jawed, Soyiba Department of Biomedical Engineering Faculty of Engineering Salim Habib University Karachi Pakistan Department of Computer Software Engineering College of Electrical and Mechanical Engineering NUST Islamabad Pakistan Department of Physics Faculty of Applied Sciences Riphah International University Islamabad Pakistan Department of Biomedical Engineering Faculty of Engineering NED University Karachi Pakistan Department of Computer Science Faculty of Information Technology Salim Habib University Karachi Pakistan

A multitude of individuals across the globe grapple with motor disabilities. Neural prosthetics utilizing Brain-computer Interface (BCI) technology exhibit promise for improving motor rehabilitation outcomes. The intricate nature of EEG data poses a significant hurdle for current BCI systems. Recently, a qualitative repository of EEG signals tied to both upper and lower limb execution of motor and motor imagery tasks has been unveiled. Despite this, the productivity of the Machine Learning (ML) Models that were trained on this dataset was alarmingly deficient, and the evaluation framework seemed insufficient. To enhance outcomes, robust feature engineering (signal processing) methodologies are implemented. A collection of time domain, frequency domain, and wavelet-derived features was obtained from 16-channel EEG signals, and the Maximum Relevance Minimum Redundancy (MRMR) approach was employed to identify the four most significant features. For classification K Nearest Neighbors, Support Vector Machine, Decision Tree, and Naive Bayes models were implemented with these selected features, evaluating their effectiveness through metrics such as testing accuracy, precision, recall, and F1 Score. By leveraging SVM with a Gaussian Kernel, a remarkable maximum testing accuracy of 92.50% for motor activities and 95.48% for imagery activities is achieved. These results are notably more dependable and gratifying compared to the previous study, where the peak accuracy was recorded at 74.36%. This research work provide an in-depth analysis of the MI Limb EEG dataset and it will help in designing and developing simple, cost-effective and reliable BCI systems for neuro-rehabilitation. © 2025, The Authors. All rights reserved.

关键词： Image enhancement

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Radiation-dominated bouncing model with slow contraction and inflation

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Physical Review D 2024年第4期109卷 043531-043531页

作者： Piero A. P. Molinari Paola C. M. Delgado Rodrigo F. Pinheiro Nelson Pinto-Neto Centro Brasileiro de Pesquisas Físicas - CBPF Rua Dr. Xavier Sigaud 150 Urca 22290-180 Rio de Janeiro RJ Brazil Faculty of Physics Astronomy and Applied Computer Science Jagiellonian University 30-348 Krakow Poland

A very simple nonsingular inflationary model is presented where the unique matter content is a radiation fluid. The model slowly contracts from a very large, almost empty and flat spacetime and realizes a bounce. It is then launched to a quasi-de Sitter inflationary expansion with more than sixty e-folds, which smoothly changes to the usual classical, decelerated radiation-dominated expansion before nucleosynthesis. The initial contracting and final expanding phases are classical, but the intermediate bounce and inflationary phases are induced by quantum cosmological effects emerging from a Gaussian wave function quickly moving in configuration space. During this quantum era, a huge number of photons is created. The scale factor describing all this rich evolution is a surprisingly simple analytic function of conformal time. The cosmological scalar perturbations arising from quantum vacuum fluctuations in the far past of the model present an almost scale invariant spectrum with an amplitude compatible with observations for reasonable values of the free parameters of the model.

关键词： Canonical quantum gravity Cosmology Inflation Quantum cosmology

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Development and study of the impacts of automated walking aids on the elderly 20

Development and study of the impacts of automated walking ai...

引用

20th International Conference on Electrical Engineering/Electronics, computer, Telecommunications and Information Technology, ECTI-CON 2023

作者： Tangjitjetsada, Maleeya Thianthong, Tawan Rakluea, Chawalit Loedhammacakra, Wisit Rakluea, Paitoon Tangthong, Nipont Mahatthanajatuphat, Chatree Chudpooti, Nonchanutt Rajamangala University of Technology Suvarnabhumi Faculty of Engineering and Architecture Department of Electronics and Telecommunication Engineering Nonthaburi Thailand Siam Airport Ground Services Co. Ltd Bangkok Thailand Rajamangala University of Technology Thanyaburi Faculty of Engineering Department of Electronics and Telecommunication Engineering Pathum Thani Thailand King Mongkut's University of Technology North Bangkok Faculty of Engineering Department of Electrical and Computer Engineering Bangkok Thailand King Mongkut's University of Technology North Bangkok Faculty of Applied Science Department of Industrial Physics and Medical Instrumentation Bangkok Thailand

ISBN: (纸本)9798350310467

Since Thailand has now completely stepped into an aged society there are more than 20% of the population aged 60 years and over. There was also an increase in those who had problems with their balance. One of the main difficulties for these people is walking on their own. This paper presents an automatic walking aid for people with balance or walking problems. A specially designed automatic walking aid can be adjusted to six levels of height. It has an anti-collision warning system at a distance of up to 40 centimeters and displays GPS coordinates via SMS when falling. The experimental results of the prototype automatic walking aid showed that the walking aid could work as designed and could help people with balance problems walk more comfortably. © 2023 IEEE.

关键词： Walking aids

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Kink movement on a periodic background

arXiv

引用

arXiv 2024年

作者： Dobrowolski, Tomasz Gatlik, Jacek Kevrekidis, Panayotis G. Department of Computer Physics and Quantum Computing University of the National Education Commission in Krakow Podchoŗ azych 2 Cracow30-084 Poland AGH University of Krakow Faculty of Physics and Applied Computer Science Krakow30-059 Poland Department of Mathematics and Statistics University of Massachusetts AmherstMA01003-4515 United States

The behavior of the kink in the sine-Gordon (sG) model in the presence of periodic inhomogeneity is studied. An ansatz is proposed that allows for the construction of a reliable effective model with two degrees of freedom. Effective models featuring very good agreement with the original field-theoretic partial differential equation are constructed, including in the non-perturbative region and for relativistic velocities. The numerical solutions of the sG model describing the evolution of the kink in the presence of a barrier as well as in the case of a periodic heterogeneity under the potential additional influence of a switched bias current and/or dissipation were obtained. The results of the field equation and the effective models were favorably compared. The effect of the choice of initial conditions in the field model on the agreement of the results with the effective model is also discussed. © 2024, CC BY.

关键词： sine-Gordon equation

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