TY - JOUR AU - Vajtai, Lili AU - Nemes, Norbert Marcel AU - Morales, Maria del Puerto AU - Molnár, Kolos AU - Pinke, Balazs Gabor AU - Simon, Ferenc TI - Incidence of the Brownian Relaxation Process on the Magnetic Properties of Ferrofluids JF - NANOMATERIALS J2 - NANOMATERIALS-BASEL VL - 14 PY - 2024 IS - 7 PG - 15 SN - 2079-4991 DO - 10.3390/nano14070634 UR - https://m2.mtmt.hu/api/publication/34801218 ID - 34801218 N1 - Department of Physics, Institute of Physics, HUN-REN-BME Condensed Matter Research Group, Budapest University of Technology and Economics, Műegyetem rkp. 3., Budapest, H-1111, Hungary Departamento de Física de Materiales, Universidad Complutense de Madrid, Madrid, 28040, Spain Department of Nanoscience and Nanotechnology, Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC), Madrid, 28049, Spain Department of Polymer Engineering, Faculty of Mechanical Engineering, Budapest University of Technology and Economics, Műegyetem rkp. 3., Budapest, H-1111, Hungary HUN–REN–BME Research Group for Composite Science and Technology, Műegyetem rkp. 3., Budapest, H-1111, Hungary MTA-BME Lendület Sustainable Polymers Research Group, Műegyetem rkp. 3., Budapest, H-1111, Hungary Institute for Solid State Physics and Optics, HUN-REN Wigner Research Centre for Physics, P.O. Box 49, Budapest, H-1525, Hungary Export Date: 22 April 2024 Correspondence Address: Nemes, N.M.; Departamento de Física de Materiales, Spain; email: nmnemes@ucm.es AB - Ferrofluids containing magnetic nanoparticles represent a special class of magnetic materials due to the added freedom of particle tumbling in the fluids. We studied this process, known as Brownian relaxation, and its effect on the magnetic properties of ferrofluids with controlled magnetite nanoparticle sizes. For small nanoparticles (below 10 nm diameter), the Neel process is expected to dominate the magnetic response, whereas for larger particles, Brownian relaxation becomes important. Temperature- and magnetic-field-dependent magnetization studies, differential scanning calorimetry, and AC susceptibility measurements were carried out for 6 and 13.5 nm diameter magnetite nanoparticles suspended in water. We identify clear fingerprints of Brownian relaxation for the sample of large-diameter nanoparticles as both magnetic and thermal hysteresis develop at the water freezing temperature, whereas the samples of small-diameter nanoparticles remain hysteresis-free down to the magnetic blocking temperature. This is supported by the temperature-dependent AC susceptibility measurements: above 273 K, the data show a low-frequency Debye peak, which is characteristic of Brownian relaxation. This peak vanishes below 273 K. LA - English DB - MTMT ER - TY - JOUR AU - Nagyfalusi, Balázs AU - Szunyogh, László AU - Palotás, Krisztián TI - Real-space nonlocal Gilbert damping from exchange torque correlation applied to bulk ferromagnets and their surfaces JF - PHYSICAL REVIEW B J2 - PHYS REV B VL - 109 PY - 2024 IS - 9 PG - 8 SN - 2469-9950 DO - 10.1103/PhysRevB.109.094417 UR - https://m2.mtmt.hu/api/publication/34749016 ID - 34749016 LA - English DB - MTMT ER - TY - JOUR AU - Nagyfalusi, Balázs AU - Udvardi, László AU - Szunyogh, László AU - Rózsa, Levente TI - Chemical potential of magnetic skyrmion quasiparticles in heavy-metal/iron bilayers JF - PHYSICAL REVIEW B J2 - PHYS REV B VL - 109 PY - 2024 IS - 9 PG - 9 SN - 2469-9950 DO - 10.1103/PhysRevB.109.094418 UR - https://m2.mtmt.hu/api/publication/34749006 ID - 34749006 LA - English DB - MTMT ER - TY - JOUR AU - Sükösd, Csaba AU - Bokor, Nándor TI - Relativisztikusan mozgó állóhullám JF - FIZIKAI SZEMLE J2 - FIZIKAI SZEMLE VL - 74 PY - 2024 IS - 2 SP - 66 EP - 70 PG - 5 SN - 0015-3257 UR - https://m2.mtmt.hu/api/publication/34738091 ID - 34738091 LA - Hungarian DB - MTMT ER - TY - JOUR AU - Márkus, Ferenc AU - Gambár, Katalin TI - Quantized Approach to Damped Transversal Mechanical Waves JF - QUANTUM REPORTS J2 - QUANTUM REPORTS VL - 6 PY - 2024 IS - 1 SP - 120 EP - 133 PG - 14 SN - 2624-960X DO - 10.3390/quantum6010009 UR - https://m2.mtmt.hu/api/publication/34719922 ID - 34719922 N1 - Department of Physics, Budapest University of Technology and Economics, Műegyetem rkp. 3, Budapest, H-1111, Hungary Department of Natural Sciences, Institute of Electrophysics, Kálmán Kandó Faculty of Electrical Engineering, Óbuda University, Tavaszmező u. 17, Budapest, H-1084, Hungary Department of Natural Sciences, National University of Public Service, Ludovika tér 2, Budapest, H-1083, Hungary Export Date: 5 April 2024 Correspondence Address: Márkus, F.; Department of Physics, Műegyetem rkp. 3, Hungary; email: markus.ferenc@ttk.bme.hu AB - In information transfer, the dissipation of a signal is of crucial importance. The feasibility of reconstructing the distorted signal depends on the related permanent loss. Therefore, understanding the quantized dissipative transversal mechanical waves might result in deep insights. In particular, it may be valid on the nanoscale in the case of signal distortion, loss, or even restoration. Based on the description of the damped quantum oscillator, we generalize the canonical quantization procedure for the case of the transversal waves. Then, we deduce the related damped wave equation and the state function. We point out the two possible solutions of the propagating-damping wave equation. One involves the well-known Gaussian spreading solution superposed with the damping oscillation, in which the loss of information is complete. The other is the Airy function solution, which is non-spreading–propagating, so the information loss is only due to oscillation damping. However, the structure of the wave shape remains unchanged for the latter. Consequently, this fact may allow signal reconstruction, resulting in the capability of restoring the lost information. LA - English DB - MTMT ER - TY - JOUR AU - Tanaka, Hayato AU - Lagzi, István László AU - Nakanishi, Hideyuki TI - In Situ Observation of Perovskite Quantum Dots Driven by Photopolymerization Controlled Using a Digital Micromirror Device (Advanced Optical Materials 5/2024) JF - ADVANCED OPTICAL MATERIALS J2 - ADV OPT MATER VL - 12 PY - 2024 IS - 5 SP - 202470012 SN - 2195-1071 DO - 10.1002/adom.202470012 UR - https://m2.mtmt.hu/api/publication/34657449 ID - 34657449 LA - English DB - MTMT ER - TY - JOUR AU - Nyáry, Anna AU - Balogh, Zoltán AU - Vigh, Máté AU - Sánta, Botond AU - Pósa, László AU - Halbritter, András Ernő TI - Voltage-time dilemma and stochastic threshold-voltage variation in pure-silver atomic switches JF - PHYSICAL REVIEW APPLIED J2 - PHYS REV APPL VL - 21 PY - 2024 IS - 1 SN - 2331-7019 DO - 10.1103/PhysRevApplied.21.014027 UR - https://m2.mtmt.hu/api/publication/34554374 ID - 34554374 N1 - Department of Physics, Institute of Physics, Budapest University of Technology and Economics (BME), Muegyetem rkp. 3, Budapest, H-1111, Hungary HUN-REN-BME Condensed Matter Research Group, Muegyetem rkp. 3., Budapest, H-1111, Hungary Institute of Technical Physics and Materials Science, HUN-REN Centre for Energy Research, Konkoly-Thege M. út 29-33, Budapest, H-1121, Hungary Export Date: 2 February 2024 Correspondence Address: Halbritter, A.; Department of Physics, Muegyetem rkp. 3, Hungary; email: halbritter.andras@ttk.bme.hu Funding details: 2022–2.1.1-NL-2022-00004, BO/00691/21, BO/00746/21, K128534, K143169, K143282 Funding details: Magyar Tudományos Akadémia, MTA, ÚNKP-22-5-BME-288, ÚNKP-22-5-BME-329 Funding details: European Regional Development Fund, ERDF Funding details: Nemzeti Kutatási Fejlesztési és Innovációs Hivatal, NKFI Funding details: Nemzeti Kutatási, Fejlesztési és Innovaciós Alap, NKFIA, VEKOP 2.3.3-15-2017-00015 Funding details: Innovációs és Technológiai Minisztérium Funding details: National Research, Development and Innovation Office Funding text 1: This research was supported by the Ministry of Culture and Innovation, the National Research, Development, and Innovation Office (NKFI) within the Quantum Information National Laboratory of Hungary (Grant No. 2022–2.1.1-NL-2022-00004) and the NKFI Grants No. K128534, No. K143169, and No. K143282. Z.B. (L.P.) acknowledges the support of the BO/00691/21 (BO/00746/21) Bolyai János Research Scholarship of the Hungarian Academy of Sciences and the ÚNKP-22-5-BME-288 (ÚNKP-22-5-BME-329) New National Excellence Program of the Ministry for Innovation and Technology from the National Research, Development, and Innovation Fund. The cryogenic measurements were supported by the helium-liquefaction plant of the BME (VEKOP 2.3.3-15-2017-00015) Competitive Central-Hungary Operative Program from the European Regional Development Fund. AB - The formation and dissolution of silver nanowires plays a fundamental role in a broad range of resistive-switching devices, which fundamentally rely on the electrochemical-metallization phenomenon. It has been shown that resistive switching may also appear in pure metallic nanowires lacking any silver-ion-hosting embedding environment but this pure atomic switching mechanism differs fundamentally from the conventional electrochemical-metallization-based resistive switching. To facilitate the quantitative description of the former phenomenon, we investigate a broad range of Ag atomic junctions, with a special focus on the frequency dependence and the fundamentally stochastic cycle-to-cycle variation of the switching-threshold voltage. These devices are established in an ultrahigh-purity environment in which electrochemical metallization can be excluded. The measured characteristics are successfully described by a vibrational-pumping model, yielding consistent predictions for the weak frequency dependence and the large variance of the switching-threshold voltage. We also demonstrate that electrochemical-metallization-based resistive switching and pure atomic switching may appear in the same device structure and therefore the proper understanding of the pure atomic switching mechanism has a very relevant importance in silver-based electrochemical-metallization cells. © 2024 American Physical Society. LA - English DB - MTMT ER - TY - JOUR AU - Fehérvári, János Gergő AU - Balogh, Zoltán AU - Török, Tímea Nóra AU - Halbritter, András Ernő TI - Noise tailoring, noise annealing, and external perturbation injection strategies in memristive Hopfield neural networks JF - APL machine learning. J2 - APL mach. learn. VL - 2 PY - 2024 IS - 1 PG - 15 SN - 2770-9019 DO - 10.1063/5.0173662 UR - https://m2.mtmt.hu/api/publication/34536907 ID - 34536907 AB - The commercial introduction of a novel electronic device is often preceded by a lengthy material optimization phase devoted to the suppression of device noise as much as possible. The emergence of novel computing architectures, however, triggers a paradigm shift in noise engineering, demonstrating that non-suppressed but properly tailored noise can be harvested as a computational resource in probabilistic computing schemes. Such a strategy was recently realized on the hardware level in memristive Hopfield neural networks, delivering fast and highly energy efficient optimization performance. Inspired by these achievements, we perform a thorough analysis of simulated memristive Hopfield neural networks relying on realistic noise characteristics acquired on various memristive devices. These characteristics highlight the possibility of orders of magnitude variations in the noise level depending on the material choice as well as on the resistance state (and the corresponding active region volume) of the devices. Our simulations separate the effects of various device non-idealities on the operation of the Hopfield neural network by investigating the role of the programming accuracy as well as the noise-type and noise amplitude of the ON and OFF states. Relying on these results, we propose optimized noise tailoring and noise annealing strategies, comparing the impact of internal noise to the effect of external perturbation injection schemes. LA - English DB - MTMT ER - TY - JOUR AU - Márkus, Ferenc AU - Gambár, Katalin TI - Symmetry Breaking and Dynamic Transition in the Negative Mass Term Klein–Gordon Equations JF - SYMMETRY (BASEL) J2 - SYMMETRY-BASEL VL - 16 PY - 2024 IS - 2 PG - 16 SN - 2073-8994 DO - 10.3390/sym16020144 UR - https://m2.mtmt.hu/api/publication/34536111 ID - 34536111 N1 - Department of Physics, Budapest University of Technology and Economics, Műegyetem rkp. 3, Budapest, H-1111, Hungary Department of Natural Sciences, Institute of Electrophysics, Kálmán Kandó, Faculty of Electrical Engineering, Óbuda University, Tavaszmező u. 17, Budapest, H-1084, Hungary Department of Natural Sciences, National University of Public Service, Ludovika tér 2, Budapest, H-1083, Hungary Export Date: 22 March 2024 Correspondence Address: Márkus, F.; Department of Physics, Műegyetem rkp. 3, Hungary; email: markus.ferenc@ttk.bme.hu Funding details: 2019-2.1.7-ERA-NET-2021-00028, TKP2021-NVA-16 Funding details: Nemzeti Kutatási Fejlesztési és Innovációs Hivatal, NKFI, K137852 Funding details: Nemzeti Kutatási, Fejlesztési és Innovaciós Alap, NKFIA Funding text 1: This research was supported by the National Research, Development and Innovation Office (NKFIH) (grant no. K137852) and by the Ministry of Innovation and Technology and NKFIH within the Quantum Information National Laboratory of Hungary. Supported by the V4-Japan Joint Research Program (BGapEng), financed by the National Research, Development and Innovation Office (NKFIH) under grant no. 2019-2.1.7-ERA-NET-2021-00028. Project no. TKP2021-NVA-16 was implemented with the support provided by the Ministry of Innovation and Technology of Hungary from the National Research, Development and Innovation Fund. AB - Through the discussion of three physical processes, we show that the Klein–Gordon equations with a negative mass term describe special dynamics. In the case of two classical disciplines—mechanics and thermodynamics—the Lagrangian-based mathematical description is the same, even though the nature of the investigated processes seems completely different. The unique feature of this type of equation is that it contains wave propagation and dissipative behavior in one framework. The dissipative behavior appears through a repulsive potential. The transition between the two types of dynamics can be specified precisely, and its physical meaning is clear. The success of the two descriptions inspires extension to the case of electrodynamics. We reverse the suggestion here. We create a Klein–Gordon equation with a negative mass term, but first, we modify Maxwell’s equations. The repulsive interaction that appears here results in a charge spike. However, the Coulomb interaction limits this. The charge separation is also associated with the high-speed movement of the charged particle localized in a small space domain. As a result, we arrive at a picture of a fast vibrating phenomenon with an electromagnetism-related Klein–Gordon equation with a negative mass term. The calculated maximal frequency value ω=1.74×1021 1/s. LA - English DB - MTMT ER - TY - JOUR AU - Német, Norbert AU - Holló, Gábor AU - Valletti, Nadia AU - Farkas, Szabolcs AU - Dúzs, Brigitta AU - Kukovecz, Ákos AU - Schuszter, Gábor AU - Szalai, István AU - Rossi, Federico AU - Lagzi, István László TI - Synthesis of zeolitic imidazolate framework-8 using an electric field in a gelled medium JF - MATERIALS ADVANCES J2 - MATER ADV VL - 5 PY - 2024 IS - 3 SP - 1199 EP - 1204 PG - 6 SN - 2633-5409 DO - 10.1039/D3MA00690E UR - https://m2.mtmt.hu/api/publication/34516454 ID - 34516454 N1 - Department of Physics, Institute of Physics, Budapest University of Technology and Economics, Műegyetem rkp 3, Budapest, H-1111, Hungary Department of Organic Chemistry and Technology, Budapest University of Technology and Economics, Műegyetem rkp 3, Budapest, H-1111, Hungary Department of Fundamental Microbiology, University of Lausanne, Biophore Building, Lausanne, 1015, Switzerland Department of Physical Sciences, Earth and Environment, University of Siena, piazzetta Enzo Tiezzi 1, Siena, 53100, Italy Department of Chemistry, University of Mainz, Duesbergweg 10-14, Mainz, 55128, Germany Interdisciplinary Excellence Center, Department of Applied and Environmental Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged, H-6720, Hungary Department of Physical Chemistry and Materials Science, University of Szeged, Rerrich Béla tér 1, Szeged, H-6720, Hungary Laboratory of Nonlinear Chemical Dynamics, Institute of Chemistry, Eötvös Loránd University, Pázmány Péter stny. 1/A, Budapest, H-1117, Hungary HU-REN-BME Condensed Matter Physics Research Group, Budapest University of Technology and Economics, Műegyetem rkp 3., Budapest, H-1111, Hungary Export Date: 19 January 2024 Correspondence Address: Lagzi, I.; Department of Physics, Műegyetem rkp 3, Hungary; email: lagzi.istvan.laszlo@ttk.bme.hu Funding details: TKP2021-EGA-02, ÚNKP-22-3-II-BME-13 Funding details: Nemzeti Kutatási Fejlesztési és Innovációs Hivatal, NKFI, K131425, K134687, K138844, K146071 Funding details: Nemzeti Kutatási, Fejlesztési és Innovaciós Alap, NKFIA Funding text 1: This work was supported by the National Research, Development and Innovation Office of Hungary (K131425, K134687, K146071, and K138844), the National Research, Development, and Innovation Fund of Hungary under the grants of TKP2021-EGA-02, and ÚNKP-22-3-II-BME-13 New National Excellence program of the Ministry for Culture and Innovation from the source of the National Research, Development and Innovation Fund. AB - Using the ion migration in various gel mediums governed by a direct electric field is a well-known technique, especially in analytical chemistry, to separate charged chemical species. This approach is also suitable for generating different-sized crystals and controlling the pattern formation in gels. Here we present a synthesis of zeolitic imidazolate framework-8 in an agarose gel driven by a direct electric field. We investigate the effect of an applied electric current on the macroscopic pattern formed in the gel, morphology, size, and dispersity of the ZIF-8 crystals. Upon increasing the electric current, the average size of the particles and dispersity of the samples decreased along the gel tube from the liquid-gel interface of the anodic side. This trend is opposite to the results obtained in synthesising particles utilizing only diffusion for mass transport. The electric field caused peak-doubling in the X-ray diffraction (XRD) pattern. To support the experimental observations, we developed a reaction-diffusion-migration model, which qualitatively describes the pattern formation observed in experiments. © 2024 RSC. LA - English DB - MTMT ER -