Article
Materials Science, Multidisciplinary
G. Bouzerar
Summary: Research shows that flat bands in two-dimensional materials can pave the way for room-temperature ferromagnetism in 2D compounds. The magnetic exchanges between localized spins are largely dominated by the ferromagnetic contribution of the flat bands, and the crossover temperatures (ferromagnetic/paramagnetic phase transition) scale linearly with the local coupling, leading to temperatures higher by an order of magnitude compared to current experimental reports. High crossover temperatures could be achieved in micrometer-sized flat band systems.
Article
Engineering, Mechanical
Andriy Prots, Matthias Voigt, Ronald Mailach
Summary: This paper introduces a new sampling method called Latinized Particle Sampling (LPS), which distributes samples uniformly in the sample space. By treating the samples as charged particles and repelling each other, a force equilibrium is achieved through iterative process, resulting in desired marginal distributions and target correlation control. Compared to regular Latin Hypercube sampling (LHS), LPS improves the quality of surrogate models and can be created much faster.
PROBABILISTIC ENGINEERING MECHANICS
(2023)
Article
Computer Science, Interdisciplinary Applications
DanHua ShangGuan
Summary: The Monte Carlo method is a powerful tool in many research fields, but the increasing complexity of physical models and mathematical models requires efficient algorithms to overcome the computational cost.
JOURNAL OF COMPUTATIONAL PHYSICS
(2021)
Article
Physics, Multidisciplinary
Aaram J. Kim, Katharina Lenk, Jiajun Li, Philipp Werner, Martin Eckstein
Summary: We propose a diagrammatic Monte Carlo approach for quantum impurity models, which is a generalization of the strong-coupling expansion for fermionic impurity models. The algorithm is based on a self-consistently computed three-point vertex and a stochastically sampled four-point vertex and provides numerically exact results in a wide parameter regime. The performance of the algorithm is demonstrated with applications to a spin-boson model representing an emitter in a waveguide. The spatial distribution of the photon density around the emitter is also discussed.
PHYSICAL REVIEW LETTERS
(2023)
Article
Physics, Multidisciplinary
Yu-Rong Shu, Shao-Kai Jian, Shuai Yin
Summary: This study investigates the nonequilibrium imaginary-time dynamics of the deconfined quantum critical point (DQCP) in the two-dimensional J-Q3 model. It finds that the spinon confinement length increases proportionally to time, rather than the usual correlation length. Additionally, it discovers that the order parameters of the Neel and the valence-bond-solid orders can be controlled by different length scales, although they satisfy the same equilibrium scaling forms. A dual dynamic scaling theory is proposed. These findings not only contribute to a new understanding of nonequilibrium criticality in DQCP, but also provide a controllable method for studying dynamics in strongly correlated systems.
PHYSICAL REVIEW LETTERS
(2022)
Article
Materials Science, Multidisciplinary
Maxime Dupont, Nicolas Laflorencie
Summary: Quantum spins on small-world networks exhibit unique behaviors compared to classical systems, with two distinct power-law behaviors for T-c versus the average strength of the extra couplings. This is influenced by a competition between characteristic length scales of the random graph and the thermal correlation length of the underlying 1D system, challenging mean-field theories. The study also explores the fate of a gapped 1D spin chain against the small-world effect.
Article
Physics, Multidisciplinary
Nikhil R. Agrawal, Rui Wang
Summary: Inhomogeneity of ion correlation is commonly found in various physicochemical, soft matter, and biological systems. This study applies the modified Gaussian renormalized fluctuation theory to investigate the vapor-liquid interface of ionic fluids, a classic example. By decomposing the ion correlation into a short-range contribution associated with the local electrostatic environment and a long-range contribution accounting for the spatially varying ionic strength and dielectric permittivity, the theory accurately predicts the coexistence curve and interfacial tension for symmetric salt, in agreement with simulation data. Additionally, the first theoretical prediction of interfacial structure for asymmetric salt is provided, emphasizing the significance of capturing local charge separation.
PHYSICAL REVIEW LETTERS
(2022)
Article
Physics, Multidisciplinary
S. Belkhatir, S. Bekhechi, B. W. Southern
Summary: We studied the 3d Heisenberg site disordered model with and without weak random anisotropy D in the presence of a uniform external longitudinal magnetic field using Monte Carlo methods. The spin and the chirality correlation lengths were measured. The study provided evidence that the mixed chiral phase is a chiral glass at a finite temperature transition TCG > 0, whereas the spin glass temperature transition is at T-SG = 0 for D = 0. In the anisotropic case, the model exhibited strong evidence of finite temperature transitions in both the spin and the chirality sectors. The estimated spin and chirality correlation-length exponents were compatible with the previous values obtained for the same model without anisotropy and the 3d Heisenberg spin glass.
PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS
(2022)
Article
Physics, Multidisciplinary
Zhenjiu Wang, Yuhai Liu, Toshihiro Sato, Martin Hohenadler, Chong Wang, Wenan Guo, Fakher F. Assaad
Summary: The study reveals new properties of the quantum spin Hall insulating state, paving the way for superconductivity through the condensation of skyrmions. Through simulations, it is confirmed that there is a direct transition between the quantum spin Hall insulator and an s-wave superconductor, with the ability to analyze dopings away from half-filling. This route to superconductivity has been proposed in the realm of twisted bilayer graphene.
PHYSICAL REVIEW LETTERS
(2021)
Article
Astronomy & Astrophysics
Francesca Cuteri, Owe Philipsen, Alena Schoen, Alessandro Sciarra
Summary: The addition of heavy dynamical quarks weakens the first-order thermal deconfinement transition in SU(3) pure gauge theory until it disappears. The critical hopping parameter and associated pion mass for lattice QCD have been calculated, with significant cutoff effects observed. The results allow for an assessment of the accuracy of the fermion determinant used in literature.
Article
Materials Science, Multidisciplinary
Kazushi Aoyama, Masaki Gen, Hikaru Kawamura
Summary: The study found that the 12 plateau appears in the magnetization curve in both models, being relatively robust against breathing bond alternation, but magnetic long-range orders are only realized in the site-phonon model. The nature characteristic of the breathing pyrochlore lattice leads to the occurrence of unconventional phases based on tetrahedra units.
Article
Materials Science, Ceramics
Lebin Liu, Jiajun Mo, Xudong Han, Weiyi Liu, Shiyu Xu, Jingzhi Liu, Min Liu
Summary: This study reported the synthesis process, structure, hyperfine parameters and magnetic properties of SmFe0.5Cr0.5O3 synthesized by the sol-gel method. The results showed that the samples exhibited nanoscale size and orthogonally distorted perovskite structure. The magnetization data and Mossbauer spectra revealed a magnetic phase transition at around 250 K.
JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY
(2022)
Article
Multidisciplinary Sciences
Roland Sandt, Robert Spatschek
Summary: Quantum annealing is an efficient technique for determining ground state configurations of binary optimization problems described by Ising Hamiltonians. In this study, we demonstrate a low-cost computational method for calculating finite temperature properties. The method is particularly effective at low temperatures, where conventional approaches suffer from high rejection rates and significant statistical noise. We validate the approach by applying it to spin glasses and Ising chains.
SCIENTIFIC REPORTS
(2023)
Article
Physics, Multidisciplinary
Massimo Ostilli, Carlo Presilla
Summary: We studied the ground state of spinless electrons interacting through a screened Coulomb potential in a lattice ring and found a first-order quantum phase transition. The critical value r(sc) and its lower and upper bounds are determined analytically, with Monte Carlo simulations estimating r(sc) to be around 2.3 at certain lattice parameters. Removal of screening leads r(sc) to tend towards zero, contrasting with the smooth crossover seen in unscreened Coulomb potential cases.
PHYSICAL REVIEW LETTERS
(2021)
Article
Spectroscopy
Shaohui Yu, Jing Liu
Summary: This paper proposes an ensemble calibration model FDA-EM-PLS (functional data analysis-ensemble learning-partial least squares) for near-infrared spectroscopy, based on the functional data analysis method. By dividing the near-infrared spectroscopy into intervals and conducting functional data analysis, clustering, and Monte Carlo sampling, this model achieves accurate detection of corn and soil data.
SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY
(2022)
Article
Nanoscience & Nanotechnology
C. Skelland, S. C. Westmoreland, T. Ostler, R. F. L. Evans, R. W. Chantrell, M. Yano, T. Shoji, A. Kato, M. Ito, M. Winklhofer, G. Zimanyi, J. Fischbacher, T. Schrefl, G. Hrkac
Article
Physics, Applied
Bradley Parks, Ahmed Abdelgawad, Thomas Wong, Richard F. L. Evans, Sara A. Majetich
PHYSICAL REVIEW APPLIED
(2020)
Article
Multidisciplinary Sciences
Mathias Augustin, Sarah Jenkins, Richard F. L. Evans, Kostya S. Novoselov, Elton J. G. Santos
Summary: Merons are nontrivial topological spin textures relevant for various phenomena in solid state physics. In the recently discovered 2D material CrCl3, merons and antimerons are shown to emerge and their dynamics are explored. This work expands the current understanding of non-trivial spin structures in 2D magnets and opens up possibilities for controlling magnetic domains through topological quasiparticles.
NATURE COMMUNICATIONS
(2021)
Article
Physics, Condensed Matter
Roberto Moreno, Sarah Jenkins, Aleksandar Skeparovski, Zlatko Nedelkoski, Alexander Gerber, Vlado K. Lazarov, Richard F. L. Evans
Summary: This study investigates the influence of anti-phase boundaries (APBs) on magnetite thin films using an atomistic spin model and identifies the new exchange interactions created in the APB as responsible for the deviation from bulk properties. The properties of magnetic materials can be tuned by controlled growth of APBs due to their density dependence on the synthesis method.
JOURNAL OF PHYSICS-CONDENSED MATTER
(2021)
Article
Physics, Applied
Ramon Cuadrado, Richard F. L. Evans, Tetsuya Shoji, Masao Yano, Akira Kato, Masaaki Ito, Gino Hrkac, Thomas Schrefl, Roy W. Chantrell
Summary: This study investigates the effects of strain on the magnetocrystalline anisotropy energy and magnetic moments of Y2Fe14B bulk alloy using density functional theory in a relativistic form. The study reveals a significant variation in the site-resolved magnetic moments for different lattice expansions and highlights the influence of the c/a ratio on the magnetocrystalline anisotropy. However, the calculated variation coupled with thermodynamic spin fluctuations cannot explain the experimentally observed increase in total magnetic anisotropy, suggesting the presence of a different physical mechanism.
JOURNAL OF APPLIED PHYSICS
(2021)
Article
Physics, Applied
N. Saenphum, J. Chureemart, R. F. L. Evans, R. W. Chantrell, P. Chureemart
Summary: This paper explores the use of GMR heads to improve reader performance by studying the effect of material properties and layer thickness on RA and MR ratio. It is found that using a Co2FeAl Heusler alloy electrode in the spin valve leads to better performance compared to conventional ferromagnetic materials. Additionally, the study considers the thickness dependence of Delta RA and its relationship with the spin diffusion length of nonmagnetic materials.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2021)
Article
Physics, Applied
Dina Abdul-Wahab, Ezio Iacocca, Richard F. L. Evans, Amilcar Bedoya-Pinto, Stuart Parkin, Kostya S. Novoselov, Elton J. G. Santos
Summary: Domain wall motion is crucial for various information technologies, and recent research has shown that in 2D vdW magnets such as CrI3 and CrBr3, domain walls can be efficiently moved by electric currents and magnetic fields. This discovery offers new possibilities for utilizing domain walls in nanodevices and has the potential to advance spintronic technology.
APPLIED PHYSICS REVIEWS
(2021)
Article
Chemistry, Physical
Ignacio M. Alliati, Richard F. L. Evans, Kostya S. Novoselov, Elton J. G. Santos
Summary: This study reports the control of magnetic domains in recently discovered 2D vdW MnPS3 antiferromagnet through magnetic fields and electric currents, achieving ultrafast domain-wall dynamics. The results indicate that the implementation of 2D antiferromagnets in real applications can be further controlled through edge engineering, providing functional characteristics for ultrathin devices with relativistic features.
NPJ COMPUTATIONAL MATERIALS
(2022)
Article
Physics, Condensed Matter
Andrea Meo, Carenza E. Cronshaw, Sarah Jenkins, Amelia Lees, Richard F. L. Evans
Summary: This paper presents a computationally efficient method for implementing spin-transfer and spin-orbit torques in micromagnetic and atomistic simulations. The author consolidates and simplifies the terminology of different kinds of torques, and introduces the spin torque as an effective magnetic field to simplify numerical implementation and interpretation of results. The approach enables faster simulations and a more direct way of interpreting the results.
JOURNAL OF PHYSICS-CONDENSED MATTER
(2023)
Article
Multidisciplinary Sciences
Sarah Jenkins, Levente Rozsa, Unai Atxitia, Richard F. L. Evans, Kostya S. Novoselov, Elton J. G. Santos
Summary: This study demonstrates that magnetic ordering can be stabilized at finite temperatures in finite-size 2D van der Waals magnets with short-range interactions, independent of magnetic anisotropy and lattice symmetry.
NATURE COMMUNICATIONS
(2022)
Article
Materials Science, Multidisciplinary
Nguyen Thanh Binh, Sergiu Ruta, Ondrej Hovorka, Richard F. L. Evans, Roy W. Chantrell
Summary: We used an atomistic model to study the dependence of the Curie temperature of L10-FePt on finite-size and surface effects in heat-assisted magnetic recording (HAMR) media. We found that there is a size threshold at 3.5 nm, below which finite-size effects start to impact the center of the grains and reduce the Curie temperature. Our study also revealed a correlation between the Curie temperature and the percentage of atomistic bonds lost on the surface as a function of grain size, which can be extended to other magnetic systems as well.
Article
Materials Science, Multidisciplinary
Sarah Jenkins, Roy W. Chantrell, Richard F. L. Evans
Summary: Antiferromagnetic materials have the potential for high-speed, high-density spintronic devices, but reliable detection of their state is challenging. Exchange bias can help with this detection. Intermixing at the interfaces between ferromagnetic and antiferromagnetic layers plays a crucial role in determining the spin state and key parameters in exchange-biased systems.
Article
Materials Science, Multidisciplinary
A. Meo, S. Sampan-a-pai, P. B. Visscher, R. Chepulskyy, D. Apalkov, J. Chureemart, P. Chureemart, R. W. Chantrell, R. F. L. Evans
Summary: The study investigates the spin transfer torque switching dynamics in CoFeB/MgO/CoFeB magnetic tunnel junctions using atomistic simulations based on Slonczewski's model. The results demonstrate a magnetization reversal driven by the combination of coherent and nonuniform excitation modes, affected by factors such as current density, temperature, and structural imperfections. This deeper understanding can be valuable for spin transfer torque dynamics in nanoscale devices.
Article
Materials Science, Multidisciplinary
Sarah Jenkins, Roy W. Chantrell, Richard F. L. Evans
Summary: Antiferromagnetic spintronic devices have the potential to outperform ferromagnetic devices due to their ultrafast dynamics and high data density. Exchange bias effect is a promising way to control antiferromagnet orientation, especially in large-scale multigranular devices. Temperature and grain size play crucial roles in determining the exchange bias, with the model confirming the existence of single antiferromagnetic domains within each grain.
Article
Materials Science, Multidisciplinary
Mara Strungaru, Matthew O. A. Ellis, Sergiu Ruta, Oksana Chubykalo-Fesenko, Richard F. L. Evans, Roy W. Chantrell
Summary: This unified model of molecular and atomistic spin dynamics allows simulations in microcanonical and canonical ensembles without the need for additional phenomenological spin damping. Energy and angular momentum transfer between the lattice and spin systems is achieved through a phenomenological coupling term representing spin-orbit interaction. The model analyzes characteristic spectra of the spin and phonon systems for different coupling strengths and temperatures, showing magnon modes and uncorrelated noise induced by lattice coupling. Investigating the effective damping parameter reveals an increase with both coupling strength and temperature, paving the way for an understanding of magnetic relaxation processes and energy transfer dynamics beyond the phenomenological approach of Gilbert damping.
