Article
Materials Science, Multidisciplinary
Sathiskumar Mariappan, Manikandan Krishnan, Dilip Bhoi, Hanming Ma, Jun Gouchi, Kapil Motla, R. P. Singh, Ponniah Vajeeston, Arumugam Sonachalam, Yoshiya Uwatoko
Summary: The effect of high pressure on the superconducting, vortex pinning, and structural properties of Re6Hf was investigated. The superconducting transition temperature shows a modest decrease with increasing pressure, and the lattice constant decreases monotonically. The upper critical field and lower critical field slightly decrease with pressure. The activation energy of vortices exhibits a double linearity field dependence. The analysis of critical current density indicates a transformation from ΔTc to Δl pinning under pressure.
Article
Chemistry, Physical
I-Hsuan Kao, Ryan Muzzio, Hantao Zhang, Menglin Zhu, Jacob Gobbo, Sean Yuan, Daniel Weber, Rahul Rao, Jiahan Li, James H. Edgar, Joshua E. Goldberger, Jiaqiang Yan, David G. Mandrus, Jinwoo Hwang, Ran Cheng, Jyoti Katoch, Simranjeet Singh
Summary: This paper demonstrates the experimental realization of field-free deterministic magnetic switching using the out-of-plane antidamping spin-orbit torque in the quantum material WTe2, and confirms this phenomenon through numerical simulations. This is of great importance for next-generation spintronic applications.
Article
Materials Science, Multidisciplinary
Sergei M. Vlasov, Grzegorz J. Kwiatkowski, Igor S. Lobanov, Valery M. Uzdin, Pavel F. Bessarab
Summary: This study demonstrates that the energy cost of spin-orbit torque induced reversal in a nanomagnet can be reduced by shaping the current pulse. Optimal switching pulses with minimized energy cost due to joule heating are derived analytically, considering reversal time and material properties. The study finds a sweet-spot balance between the fieldlike and dampinglike components of spin-orbit torque, allowing for efficient switching using a down-chirped rotating current pulse.
Article
Chemistry, Physical
D. C. Mahendra, Ding-Fu Shao, Vincent D. -H. Hou, Arturas Vailionis, P. Quarterman, Ali Habiboglu, M. B. Venuti, Fen Xue, Yen-Lin Huang, Chien-Min Lee, Masashi Miura, Brian Kirby, Chong Bi, Xiang Li, Yong Deng, Shy-Jay Lin, Wilman Tsai, Serena Eley, Wei-Gang Wang, Julie A. Borchers, Evgeny Y. Tsymbal, Shan X. Wang
Summary: By utilizing unconventional spins generated in a MnPd3 thin film grown on an oxidized silicon substrate, the authors observed both conventional spin-orbit torques and unconventional out-of-plane and in-plane anti-damping-like torques in MnPd3/CoFeB heterostructures, enabling complete field-free switching of perpendicular cobalt. These unconventional torques are attributed to the low symmetry of the (114)-oriented MnPd3 films. The results provide a path towards practical spin channels in ultrafast magnetic memory and logic devices.
Article
Physics, Multidisciplinary
J. E. Hirsch, F. Marsiglio
Summary: The Meissner effect, magnetic field expulsion, is a hallmark of superconductivity. Recent studies claimed to have found definitive evidence of the Meissner effect in sulfur hydride and lanthanum hydride under high pressure, but we argue that the evidence presented does not support the case for superconductivity in these materials. Combining previous experimental evidence, we strongly suggest that hydrides under pressure are not high-temperature superconductors.
MATTER AND RADIATION AT EXTREMES
(2022)
Article
Physics, Applied
Y. Tsui, D. A. Moseley, A. R. Dennis, Y-H Shi, M. R. Beck, V Cientanni, D. A. Cardwell, J. H. Durrell, M. D. Ainslie
Summary: Bulk high-temperature superconducting materials can trap magnetic fields up to an order of magnitude larger than conventional permanent magnets. Recent advances in pulsed field magnetization techniques have allowed for the fast and cost-effective magnetization of these materials to fields of up to 5 T. Researchers have developed a portable, desktop magnet system that combines advanced pulsed field magnetization techniques with cryocooler technology and single-grain bulk superconducting materials. This system is capable of trapping magnetic fields of up to about 3 T.
SUPERCONDUCTOR SCIENCE & TECHNOLOGY
(2022)
Article
Materials Science, Multidisciplinary
Stanislaw Lazarski, Witold Skowronski, Krzysztof Grochot, Wieslaw Powroznik, Jaroslaw Kanak, Marek Schmidt, Tomasz Stobiecki
Summary: The study investigates the spin-orbit torque induced magnetization switching in a CoFeB/Ta/CoFeB trilayer, with modifications in interlayer exchange coupling and magnetic anisotropy axes orientation by varying the thickness of the heavy metal Ta spacer. The control of CoFeB layer magnetization state and the increase in SOT induced critical current density with decreasing Ta spacer thickness are crucial factors in achieving field-free magnetization switching.
Editorial Material
Multidisciplinary Sciences
J. E. Hirsch
Summary: Contrary to the current consensus, the author argues that the existing evidence for high-temperature superconductivity in hydrides under high pressure is not convincing. The author suggests that the focus of research should urgently shift to experimentally establish whether or not superconductivity exists in pressurized hydrides, instead of searching for new materials that may show unproven superconductivity signals at higher temperatures. The implications of a negative finding for the theoretical understanding of superconductivity are discussed.
NATIONAL SCIENCE REVIEW
(2023)
Article
Engineering, Electrical & Electronic
Jeongchun Ryu, Ryan Thompson, Jae Yeol Park, Seok-Jong Kim, Gaeun Choi, Jaimin Kang, Han Beom Jeong, Makoto Kohda, Jong Min Yuk, Junsaku Nitta, Kyung-Jin Lee, Byong-Guk Park
Summary: Spin-orbit coupling converts charge current into spin current, generating spin-orbit torque. Previous studies only used part of the polarization of the spin current, while this study demonstrates a method that utilizes all three polarizations. This approach reduces the switching current for field-free spin-orbit torque and is applicable for mass production.
NATURE ELECTRONICS
(2022)
Article
Physics, Applied
Krzysztof Grochot, Lukasz Karwacki, Stanislaw Lazarski, Witold Skowronski, Jaroslaw Kanak, Wieslaw Powroznik, Piotr Kuswik, Mateusz Kowacz, Feliks Stobiecki, Tomasz Stobiecki
Summary: This study investigates magnetization switching induced by spin-orbit torque in W (Pt)/Co/NiO heterostructures. The research demonstrates deterministic Co magnetization switching without the need for an external magnetic field, instead using an in-plane exchange-bias field. The effective spin Hall angle in the W-based system is found to be higher than in the Pt-based system, resulting in a higher relative difference in resistance states during magnetization current switching.
PHYSICAL REVIEW APPLIED
(2021)
Article
Physics, Applied
T. Oka, K. Sudo, J. L. Dadiel, N. Sakai, H. Seki, M. Miryala, M. Murakami, T. Nakano, M. Ooizumi, K. Yokoyama, M. Tsujimura
Summary: This article introduces a unique magnetic separation technique using high temperature superconducting bulk magnet to collect nickel sulfate crystals from nickel-plating waste liquid. This method offers a novel way for recycling nickel resources.
SUPERCONDUCTOR SCIENCE & TECHNOLOGY
(2022)
Article
Materials Science, Multidisciplinary
Vage Karakhanyan, Clement Eustache, Yannick Lefier, Thierry Grosjean
Summary: This paper reveals that the orbital angular momentum (OAM) of light plays a significant role in the inverse Faraday effect (IFE), and the control of spin and orbital angular momentum of light can impact the optomagnetic field, potentially affecting fields such as all-optical magnetization switching and spin-wave excitation.
Article
Materials Science, Multidisciplinary
A. A. Tereshchenko, A. S. Ovchinnikov, D. I. Gorbunov, D. S. Neznakhin
Summary: This study discusses the possibility of experimentally observing ultrasonic attenuation in the ferromagnet LuCo3 near the low-spin-high-spin crossover. The researchers show that ultrasound propagation in the material leads to transitions between magnon band states through the absorption of phonons, and this process is highly sensitive to the magnetization value. The presence of a high magnetic field alters the ultrasound propagation regime from off-resonant to resonant, and the researchers propose a criterion for this change. Calculations demonstrate anomalies in the temperature and field dependence of ultrasonic wave number and attenuation near the crossover point at intermediate temperatures far below the Curie temperature.
Article
Physics, Applied
Mustafa Akyol, Guoqiang Yu, Kin Wong, Kang L. Wang
Summary: By studying the Pt/Ta(wedge)/CoFeB/MgO multilayer structure, we demonstrated the technique of current-driven perpendicular magnetization switching using spin-orbit torque, achieved by breaking the structural symmetry to enable switching without the need for a magnetic field.
APPLIED PHYSICS LETTERS
(2022)
Article
Chemistry, Multidisciplinary
Vijay S. Parmar, Andreas M. Thiel, Marie S. Norre, Jacob Overgaard
Summary: The temperature and pressure dependence of a high-performing single molecule magnet, [Dy(Mes*O)(2)(THF)2Br] (1), have been studied. A new polymorph of 1 was observed under pressure and at low temperatures. The distances and energies of the first Kramers doublets remained mostly unchanged, regardless of phase changes and external pressure. The calculated energy barrier to magnetic reversal varied without a clear trend as pressure increased.
CRYSTAL GROWTH & DESIGN
(2023)
Article
Chemistry, Physical
A. A. Vaulin, A. M. Chirkova, E. A. Sherstobitova, D. A. Shishkin, E. M. Sherokalova, K. P. Skokov, N. Baranov, A. F. Gubkin
Summary: The magnetic properties, thermal expansion, heat capacity, and electrical resistivity of the cluster-glass compound Er4.8Pd2 were studied. Short-range antiferromagnetic correlations were observed in the localized magnetic moments of Er3+ ions, leading to the observation of a cluster-glass magnetic state. The crystal electric field (CEF) substantially affected the heat capacity and thermal expansion of Er4.8Pd2.
Article
Materials Science, Multidisciplinary
D. S. Neznakhin, A. S. Bolyachkin, M. Bartashevich, L. V. B. Diop, O. Gutfleisch, K. P. Skokov
Summary: A remarkable feature of high anisotropy intermetallic compounds is the difference of saturation magnetization along different magnetization axes, which needs to be considered in the evaluation of magnetization curves. Our experimental study on the angular dependence of saturation magnetization in a Y2Co7 single crystal verifies the assumption.
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
(2022)
Article
Materials Science, Multidisciplinary
Heike C. Herper, Konstantin P. Skokov, Semih Ener, Patrik Thunstroem, Leopold V. B. Diop, Oliver Gutfleisch, Olle Eriksson
Summary: This study presents a comprehensive theoretical and experimental investigation of the magnetic properties of NdFe11Ti and RE-free YFe11Ti, aiming to elucidate the influence of the 4f electrons. The localized 4f electrons of Nd are found to be the driving force behind the complex magnetocrystalline anisotropy behavior, transitioning from cone to uniaxial above 170 K. The experimental data are compared with density functional theory, supplemented with a Hartree-Fock correction (+U) and an approximate dynamical mean-field theory.
Article
Materials Science, Multidisciplinary
Yuxiao Jia, Yuye Wu, Yichen Xu, Ruixiao Zheng, Shiteng Zhao, Konstantin P. Skokov, Fernando Maccari, Alex Aubert, Oliver Gutfleisch, Jingmin Wang, Hui Wang, Jianxin Zou, Chengbao Jiang
Summary: In this study, a strategy to suppress twin formation in L1(0)-MnAl permanent magnets was proposed by reducing the grain and/or particle sizes below a critical size of D-t-300 nm. The results showed that the optimal coercivity can be achieved within the range of 50-200 nm, providing a pathway to achieve a twin-free microstructure with high texture degree in polymer-bonded or sintered magnets. These findings can be applied to other twin-containing permanent magnet compounds to increase their texture and maximal energy products.
Article
Materials Science, Ceramics
A. Aubert, J. S. Garitaonandia, F. Maccari, J. Broetz, K. Skokov, O. Gutfleisch
Summary: Recent research has shown that uniaxial magnetic anisotropy can be induced in Cobalt ferrite (CFO) by reactive sintering using spark plasma sintering (SPS), improving its magnetostrictive properties. This study investigates the parameters responsible for the induced anisotropy and identifies that it arises during cooling under SPS's uniaxial compression. Additionally, the study explores the fundamental origin of the magnetic anisotropy and find that it is caused by the ionic distribution of Co2+ in the CFO's spinel lattice. These findings advance the understanding of the relationship between SPS processing and magnetic properties of cobalt ferrite.
CERAMICS INTERNATIONAL
(2023)
Article
Materials Science, Multidisciplinary
Franziska Staab, Enrico Bruder, Lukas Scha, Konstantin Skokov, David Koch, Benjamin Zingsem, Esmaeil Adabifiroozjaei, Leopoldo Molina-Luna, Oliver Gutfleisch, Karsten Durst
Summary: Textured nanocrystalline SmCo5-Cu magnets are produced by high-pressure torsion (HPT) of powder blends consisting of SmCo5 and Cu powder. The process overcomes limitations imposed by the phase diagram as in conventional sintering routes, enabling a free selection of the magnetic phase and the grain boundary phase. Increasing number of rotations during HPT leads to structural refinement, increasing coercivity, and amorphous structure of strongly deformed SmCo5 particles. The magnetic hardening is attributed to microstructural refinement and magnetic decoupling of hard magnetic SmCo5 grains by Cu.
Article
Physics, Applied
Jianing Liu, Ruiwen Xie, Alex Aubert, Lukas Schaefer, Hongbin Zhang, Oliver Gutfleisch, Konstantin Skokov
Summary: The understanding of the coercivity mechanism in Nd-Fe-B permanent magnets relies on the analysis of magnetic properties of all phases present in the magnets. In this study, Nd6Fe13Cu single crystals were grown and their magnetic properties were studied. It was observed that Nd6Fe13Cu is antiferromagnetic below the Neel temperature and exhibits a spin-flop transition in a magnetic field. Atomistic spin dynamics simulation confirmed the change in antiferromagnetic coupling between Nd layers above and below the Cu layers, which causes the spin-flop transition. These findings suggest that the role of the Nd6Fe13Cu grain boundary phase in the coercivity enhancement of Nd-Fe-B-Cu magnets is more complex than previously thought.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Applied
Benedikt Beckmann, Tarek A. El-Melegy, David Koch, Ulf Wiedwald, Michael Farle, Fernando Maccari, Joshua Snyder, Konstantin P. Skokov, Michel W. Barsoum, Oliver Gutfleisch
Summary: Reactive single-step hot-pressing at high temperature and pressure can produce dense, near single-phase Fe-based MAB samples with favorable magnetocaloric properties. Ge and Ga doping can tailor the magnetic and magnetocaloric properties, increasing the Curie temperature and spontaneous magnetization. The hot-pressed samples show a second-order magnetic phase transition and have potential applications in low-cost and low-criticality magnetocaloric devices around room temperature.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Applied
Franziska Scheibel, Wei Liu, Lukas Pfeuffer, Navid Shayanfar, Andreas Taubel, Konstantin P. Skokov, Stefan Riegg, Yuye Wu, Oliver Gutfleisch
Summary: This study compares the properties of single-phase Ni-Mn-In alloys and two-phase Gd-doped Ni-Mn-In alloys and finds that the addition of Gd has little effect on the magnetocaloric performance, but greatly improves the mechanical stability by causing grain refinement.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Energy & Fuels
Wei Liu, Tino Gottschall, Franziska Scheibel, Eduard Bykov, Nuno Fortunato, Alex Aubert, Hongbin Zhang, Konstantin Skokov, Oliver Gutfleisch
Summary: Magnetocaloric hydrogen liquefaction has the potential to revolutionize the liquid hydrogen industry. Light rare-earth based materials offer a more sustainable alternative to heavy rare-earth compounds, with higher abundances and greater magnetocaloric effects in the required temperature range. By tuning the Curie temperature of light rare-earth alloys and mixing different rare-earth elements, a fully light rare-earth intermetallic series is developed, showcasing competitive maximum effects for hydrogen liquefaction compared to heavy rare-earth compounds like DyAl2.
JOURNAL OF PHYSICS-ENERGY
(2023)
Article
Materials Science, Multidisciplinary
K. Schafer, R. G. T. Fim, F. Maccari, T. Braun, S. Riegg, K. P. Skokov, D. Koch, E. Bruder, I. Radulov, C. H. Ahrens, P. A. P. Wendhausen, O. Gutfleisch
Summary: Nd-Fe-B bonded magnets are important for various technological applications. Additive Manufacturing allows the fabrication of net-shape bonded magnets with complex geometries, tailored for specific applications. This study presents a technique using Laser Powder Bed Fusion to fabricate anisotropic bonded magnets without the need for a magnetic field source.
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
(2023)
Article
Physics, Applied
K. P. Skokov, A. Y. Karpenkov, D. Y. Karpenkov, I. A. Radulov, D. Guenzing, B. Eggert, A. Rogalev, F. Wilhelm, J. Liu, Y. Shao, K. Ollefs, M. E. Gruner, H. Wende, O. Gutfleisch
Summary: Alloys with a first-order magnetic transition play a crucial role in solid-state refrigeration technology, sensors and actuators, and spintronic devices. The discontinuous nature of the transition in these materials is due to the coupling between the magnetic, electronic, and structural subsystems.
APPLIED PHYSICS REVIEWS
(2023)
Article
Chemistry, Multidisciplinary
Imants Dirba, Yevhen Ablets, Konstantin Skokov, Esmaeil Adabifiroozjaei, Leopoldo Molina-Luna, Oliver Gutfleisch
Summary: The production of bulk nanostructured silicide thermoelectric materials by a reversible hydrogen absorption-desorption process is demonstrated. The advanced synthesis process enables microstructure refinement of more than two orders of magnitude and formation of fine precipitates. This method has the potential to reduce thermal conductivity and is environmentally friendly.
Article
Materials Science, Multidisciplinary
A. F. Gubkin, A. A. Vaulin, T. Tsutaoka, A. F. Prekul, K. P. Skokov, N. V. Baranov
Summary: The crystal structure, thermal properties, and magnetic state of the rare-earth intermetallic compound Ho7Rh3 were studied. An incommensurate antiferromagnetic (AFM) structure was observed below a certain temperature, and short-range AFM correlations were found to affect the magnetic susceptibility and thermal expansion.
Article
Engineering, Electrical & Electronic
Alex Aubert, Konstantin Skokov, Gabriel Gomez, Alisa Chirkova, Iliya Radulov, Fabrice Wilhelm, Andrei Rogalev, Heiko Wende, Oliver Gutfleisch, Katharina Ollefs
Summary: We present a new instrument for advanced magnetic studies, which is based on the high field X-ray magnetic circular dichroism end-station developed at the European Synchrotron Radiation Facility. This instrument offers the unique possibility to measure element-specific and macroscopic properties related to magnetic, electronic, and structural degrees of freedom of magnetic materials.
IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT
(2022)
