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Magnetic anisotropy of the van der Waals ferromagnet Cr2Ge2Te6 studied by angular-dependent x-ray magnetic circular dichroism

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Physical Review Research 2022年第1期4卷 013139-013139页

作者： M. Suzuki B. Gao G. Shibata S. Sakamoto Y. Nonaka K. Ikeda Z. Chi Y.-X. Wan T. Takeda Y. Takeda T. Koide A. Tanaka M. Kobayashi S.-W. Cheong A. Fujimori Department of Physics The University of Tokyo Bunkyo-ku Tokyo 113-0033 Japan Rutgers Center for Emergent Materials and Department of Physics and Astronomy Rutgers University Piscataway New Jersey 08854 USA Department of Applied Physics Tokyo University of Science Katsushika-ku Tokyo 125-8585 Japan Department of Electrical Engineering and Information Systems The University of Tokyo Bunkyo-ku Tokyo 113-8656 Japan Materials Sciences Research Center Japan Atomic Energy Agency (JAEA) Sayo Hyogo 679-5148 Japan Photon Factory Institute of Materials Structure Science High Energy Accelerator Research Organization Tsukuba Ibaraki 305-0801 Japan Quantum Matter Program Graduate School of Advanced Science and Engineering Hiroshima University Higashi-hiroshima 739-8530 Japan Center for Spintronics Research Network The University of Tokyo Bunkyo-ku Tokyo 113-0033 Japan Department of Applied Physics Waseda University Shinjuku-ku Tokyo 169-8555 Japan

The van der Waals ferromagnet Cr2Ge2Te6 (CGT) has a two-dimensional crystal structure where each layer is stacked through van der Waals force. We have investigated the nature of the ferromagnetism and the weak perpendicular magnetic anisotropy (PMA) of CGT by means of x-ray absorption spectroscopy and x-ray magnetic circular dichroism (XMCD) studies of CGT single crystals. The XMCD spectra at the Cr L2,3 edge for different magnetic field directions were analyzed on the basis of the cluster-model multiplet calculation. The Cr valence is confirmed to be 3+ and the orbital magnetic moment is found to be nearly quenched, as expected for the high-spin t2g3 configuration of the Cr3+ ion. A large (∼0.2 eV) trigonal crystal-field splitting of the t2g level caused by the distortion of the CrTe6 octahedron has been revealed, while the single-ion anisotropy (SIA) of the Cr atom is found to have a sign opposite to the observed PMA and too weak compared to the reported anisotropy energy. The present result suggests that anisotropic exchange coupling between the Cr atoms through the ligand Te 5p orbitals having strong spin-orbit coupling has to be invoked to explain the weak PMA of CGT, as in the case of the strong PMA of CrI3.

关键词： Electronic structure Magnetic anisotropy 2-dimensional systems Magnetic semiconductors Cluster models X-ray magnetic circular dichroism

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Facile Synthesis of Ni2+ Doped Mgfe2o4 Spinel Nanoparticles: Structural, Optical, Magnetic, and Dielectric Behavior

SSRN

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SSRN 2023年

作者： Revathi, R. Sukumar, M. Ubaidullah, Mohd Gupta, Manish Sehgal, Satbir Singh Udhaya, M.P. Aji Pandit, Bidhan Sundararajan, M. Subramani, M.A. Dash, Chandra Sekhar Department of Biotechnology Periyar University Centre for Post Graduate and Research Studies Tamil Nadu Dharmapuri636 205 India Department of Applied Physics Sri Venkateswara College of Engineering Pennalur Tamil Nadu Sriperumbudur602 117 India Department of Chemistry College of Science King Saud University P.O. Box 2455 Riyadh11451 Saudi Arabia Division of Research and Development Lovely Professional University Punjab India Department of Physics Holy Cross College Nagercoil629 004 India Department of Materials Science and Engineering and Chemical Engineering Universidad Carlos III de Madrid Avenida de la Universidad 30 Leganés Madrid28911 Spain PG & Research Department of Physics Paavendhar College of Arts & Science M.V. South Thalaivasal Tamilnadu Salem636 121 India Department of Chemistry Apollo Arts and Sciences College Poonamallee Chennai602 106 India Department of Electronics and Communication Engineering Centurion University of Technology and Management Odisha Bhubaneswar752050 India Chandigarh University India

Nickel doped magnesium cubic spinel ferrite nanoparticles (NPs) were prepared through microwave combustion method (MCM). The structure of magnesium ferrite normal spinel is obtained from XRD analysis. The average crystallite size is between 26 and 17 nm. The elemental compositions and oxidizing states of Ni2+ doped MgFe2O4 ferrites were evaluated by using XPS analysis. Morphology of spinel nanoparticles were studied using HR-SEM images. The energy dispersive X-ray method is used for ensuring the presence of elements and the band gap value 2.09, 2.02, 1.85 and 1.82 eV have obtained using the tau’c relation. The magnesium spinel structure is confirmed the band at 434 and 561 cm-1 which corresponds to the stretching vibration of octahedral site (Mg2+ -O2-) and tetrahedral site (Fe3+ -O2-) respectively. From the hysteresis loops the magnetic features viz. Hc, Mr and Ms were determined. Further dielectric studies and AC conductivity of the prepared samples is performed. © 2023, The Authors. All rights reserved.

关键词： Surface chemistry

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Angle-resolved photoemission spectroscopy with an in situ tunable magnetic field

arXiv

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arXiv 2023年

作者： Huang, Jianwei Yue, Ziqin Baydin, Andrey Zhu, Hanyu Nojiri, Hiroyuki Kono, Junichiro He, Yu Yi, Ming Department of Physics and Astronomy Rice University HoustonTX77005 United States Applied Physics Graduate Program Smalley-Curl Institute Rice University HoustonTX77005 United States Department of Electrical and Computer Engineering Rice University HoustonTX77005 United States Smalley–Curl Institute Rice University HoustonTX77005 United States Department of Materials Science and NanoEngineering Rice University HoustonTX77005 United States Institute for Materials Research Tohoku University Katahira 2-1-1 Sendai980-8577 Japan Department of Applied Physics Yale University New HavenCT06511 United States

Angle-resolved photoemission spectroscopy (ARPES) is a powerful tool for probing the momentum-resolved single-particle spectral function of materials. Historically, in situ magnetic fields have been carefully avoided as they are detrimental to the control of photoelectron trajectory during the photoelectron detection process. However, magnetic field is an important experimental knob for both probing and tuning symmetry-breaking phases and electronic topology in quantum materials. In this paper, we introduce an easily implementable method for realizing an in situ tunable magnetic field at the sample position in an ARPES experiment and analyze magnetic field induced artifacts in ARPES data. Specifically, we identified and quantified three distinct extrinsic effects of a magnetic field: Constant energy contour rotation, emission angle contraction, and momentum broadening. We examined these effects in three prototypical quantum materials, i.e., a topological insulator (Bi2Se3), an iron-based superconductor (LiFeAs), and a cuprate superconductor (Pb-Bi2Sr2CuO6+x), and demonstrate the feasibility of ARPES measurements in the presence of a controllable magnetic field. Our studies lay the foundation for the future development of the technique and interpretation of ARPES measurements of field-tunable quantum phases. Copyright © 2023, The Authors. All rights reserved.

关键词： Photoelectrons

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Stacking-fault networks with Lomer-Cottrell locks induced by carbon addition in a severely strained Cr-Co-Ni alloy

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Journal of Alloys and Compounds 2025年 1033卷

作者： Stumpf, Guilherme Cardeal Bertoli, Gustavo Coury, Francisco Gil Neta, Augusta Cerceau Isaac Montoro, Luciano Andrey Figueiredo, Roberto Braga Wolf, Witor Graduate Program in Metallurgical Materials and Minning Engineering Federal University of Minas Gerais MG Belo Horizonte31270-901 Brazil Graduate Program in Materials Science and Engineering Federal University of São Carlos Rod. Washington Luiz Km 235 SP São Carlos13565-905 Brazil Department of Materials Engineering Federal University of São Carlos SP São Carlos13565-905 Brazil Department of Metallurgical and Materials Engineering Federal University of Minas Gerais Av. Antônio Carlos 6627 MG Belo Horizonte31270-901 Brazil Department of Chemistry Federal University of Minas Gerais Av. Antônio Carlos 6627 MG Belo Horizonte31270-901 Brazil SP São Carlos13563-120 Brazil

Face-centered cubic (FCC) Cr-Co-Ni multi-principal element alloys are among the toughest materials ever designed. The optimal trade-off between strength and ductility shown by these materials is tied with their deformation evolution. Typically, their plastic deformation starts with dislocation slip, followed by mechanical twinning (i.e., twinning induced plasticity, TWIP) and, as strain levels further increase, phase transformation induced by plasticity (TRIP). This work evaluates the deformation substructure of a highly strained (achieved with high-pressure torsion) Cr40Co30Ni30 (at%) alloy with and without carbon alloying. After processing, the carbon-free alloy developed a typical substructure observed in FCC Medium/High-entropy alloys at later stages of straining, characterized by the presence of nanotwins and HCP lamellae, resulting in a 5.9 GPa hardness. In contrast, carbon addition induced grain refinement and suppression of the TWIP and TRIP effects. Notably, the Cr39.6Co30Ni30C0.4 alloy developed networks of stacking faults with partial dislocations and Lomer-Cottrell locks, which primarily contributed to a stronger hardening capability, resulting in an increased hardness of 7.3 ± 0.8 GPa, 22 % (1.3 GPa) higher than the base alloy. These findings have important implications for better understanding the deformation substructure evolution of FCC multi-principal element alloys and can pave the way forward in regard to the design approaches for carbon-alloying in these materials. © 2025 Elsevier B.V.

关键词： Plastic flow

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Loss tangent fluctuations due to two-level systems in superconducting microwave resonators

arXiv

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arXiv 2024年

作者： Vallières, André Russell, Megan E. You, Xinyuan Garcia-Wetten, David A. Goronzy, Dominic P. Walker, Mitchell J. Bedzyk, Michael J. Hersam, Mark C. Romanenko, Alexander Lu, Yao Grassellino, Anna Koch, Jens McRae, Corey Rae H. Graduate Program in Applied Physics Northwestern University EvanstonIL60208 United States Fermi National Accelerator Laboratory BataviaIL60510 United States Department of Physics and Astronomy Northwestern University EvanstonIL60208 United States Department of Materials Science and Engineering Northwestern University EvanstonIL60208 United States Department of Chemistry Northwestern University EvanstonIL60208 United States Department of Electrical and Computer Engineering Northwestern University EvanstonIL60208 United States Center for Applied Physics and Superconducting Technologies Northwestern University EvanstonIL60208 United States Electrical Computing and Energy Engineering Department University of Colorado BoulderCO80309 United States Department of Physics University of Colorado BoulderCO80309 United States National Institute of Standards and Technology BoulderCO80305 United States

Superconducting microwave resonators are critical to quantum computing and sensing technologies. Additionally, they are common proxies for superconducting qubits when determining the effects of performance-limiting loss mechanisms such as from two-level systems (TLS). The extraction of these loss mechanisms is often performed by measuring the internal quality factor Qi as a function of power or temperature. In this work, we investigate large temporal fluctuations of Qi at low powers over periods of 12 to 16 hours (relative standard deviation σQi/Qi = 13%). These fluctuations are ubiquitous across multiple resonators, chips and cooldowns. We are able to attribute these fluctuations to variations in the TLS loss tangent due to two main indicators. First, measured fluctuations decrease as power and temperature increase. Second, for interleaved measurements, we observe correlations between low- and medium-power Qi fluctuations and an absence of correlations with high-power fluctuations. Agreement with the TLS loss tangent mean is obtained by performing measurements over a time span of a few hours. We hypothesize that, in addition to decoherence due to coupling to individual near-resonant TLS, superconducting qubits are affected by these observed TLS loss tangent fluctuations. © 2024, CC BY.

关键词： Qubits

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Incommensurate magnetic orders and topological Hall effect in the square-net centrosymmetric EuGa2Al2 system

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Physical Review materials 2022年第7期6卷 074201-074201页

作者： Jaime M. Moya Shiming Lei Eleanor M. Clements Caitlin S. Kengle Stella Sun Kevin Allen Qizhi Li Y. Y. Peng Ali A. Husain Matteo Mitrano Matthew J. Krogstad Raymond Osborn Anand B. Puthirath Songxue Chi L. Debeer-Schmitt J. Gaudet P. Abbamonte Jeffrey W. Lynn E. Morosan Applied Physics Graduate Program Smalley-Curl Institute Rice University Houston Texas 77005 USA Department of Physics and Astronomy Rice University Houston Texas 77005 USA NIST Center for Neutron Research National Institute of Standards and Technology Gaithersburg Maryland 20899 USA Department of Physics University of Illinois at Urbana-Champaign Urbana Illinois 61801 USA International Center for Quantum Materials School of Physics Peking University CN-100871 Beijing China Department of Physics and Astronomy and Quantum Matter Institute University of British Columbia Vancouver British Columbia Canada V6T 1Z1 Department of Physics Harvard University Cambridge Massachusetts 02138 USA Materials Science Division Argonne National Laboratory Lemont Illinois 60439 USA Department of Materials Science and NanoEngineering Rice University Houston Texas 77005 USA Neutron Scattering Division Oak Ridge National Laboratory Oak Ridge Tennessee 37831 USA Department of Materials Science and Engineering University of Maryland College Park Maryland 20742-2215 USA

Neutron diffraction on the centrosymmetric square-net magnet EuGa2Al2 reveals multiple incommensurate magnetic states (AFM1, 2, 3) in zero field. In applied field, a new magnetic phase (A) is identified from magnetization and transport measurements, bounded by two of the μ0H=0 incommensurate magnetic phases (AFM1, helical, and AFM3, cycloidal) with different moment orientations. Moreover, magnetotransport measurements indicate the presence of a topological Hall effect, with maximum values centered in the A phase. Together, these results render EuGa2Al2 a material with noncoplanar or topological spin texture in applied field. X-ray diffraction reveals an out-of-plane (OOP) charge density wave (CDW) below TCDW∼50 K while the magnetic propagation vector lies in plane below TN=19.5 K. Together these data point to a new route to realizing in-plane noncollinear spin textures through an OOP CDW. In turn, these noncollinear spin textures may be unstable against the formation of topological spin textures in an applied field.

关键词： Charge density waves Exotic phases of matter Hall effect Magnetic phase transitions Magnetotransport Symmetry protected topological states Topological materials

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Zirconium Diboride as the Protective Layer for Stable Aqueous Zinc-Ion Batteries with Long Cycle Life

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Electrochimica Acta 2025年 535卷

作者： Fang-Chia Kuo Hsin-I Tsai Tuan-Yue Lin Fan-Wei Liu Yu-Ze Chen Department of Materials Science and Engineering National Cheng Kung University Tainan City 70101 Taiwan Graduate Degree Program in Semiconductor and Green Technology Academy of Circular Economy National Chung Hsing University. Taichung City 40202 Taiwan Program on Key Materials Academy of Innovative Semiconductor and Sustainable Manufacturing National Cheng Kung University Tainan City 70101 Taiwan Program on Semiconductor Packaging and Testing Academy of Innovative Semiconductor and Sustainable Manufacturing National Cheng Kung University Tainan City 70101 Taiwan

Integrating intermittent renewable energy sources with battery energy storage systems is imperative to achieve sustainable development and net-zero emissions. Despite widespread adoption, lithium-ion batteries (LIBs) face inherent challenges, including safety concerns and environmental pollution. In contrast, aqueous zinc-ion batteries (AZIBs) have garnered significant attention due to their intrinsic non-flammability, cost-effectiveness, and environmental compatibility. However, the practical application of Zn foil anodes is hindered by issues such as non-uniform Zn deposition and severe corrosion, which degrade battery performance and longevity. This study investigates zirconium diboride (ZrB₂) as a protective coating for Zn anodes to mitigate dendritic challenges and enhance battery lifespan. Coating the ZrB₂ layer on the Zn anode significantly reduces the nucleation overpotential to 23.8 mV and enables stable cycling of symmetrical cells for 4500 hours at a current density of 1 mA cm⁻² and an areal capacity of 0.5 mA h cm⁻². Furthermore, the ZrB₂@Zn//VOx pouch cell exhibits stable cycling for 600 cycles under various bending conditions without short-circuit failure, demonstrating superior mechanical flexibility and reliability. This work introduces ZrB₂ as a promising protective material for high-performance AZIBs and provides valuable insights into the application of ceramic coatings for stabilizing Zn anodes, paving the way for the advancement of next-generation aqueous energy storage systems.

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Correction: Advancements in additive manufacturing for video laryngoscopes: a comprehensive scoping and technological review

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Systematic reviews 2024年第1期13卷 31页

作者： Ana Cristina Beitia Kraemer Moraes Chiara das Dores do Nascimento Everton Granemann Souza Mauricio Beitia Kraemer Mauricio Moraes Neftali Lenin Villarreal Carreno Evandro Piva Rafael Guerra Lund Pelotas Dental School Graduate Program in Dentistry Federal University of Pelotas Pelotas RS 96010‑560 Brazil. Master's Degree in Electronic and Computer Engineering Center for Social and Technological Sciences Catholic University of Pelotas Pelotas RS 96015‑560 Brazil. Faculty of Medicine São Francisco University Bragança Paulista SP 12916‑900 Brazil. Faculty of Medicine Federal University of Pelotas Pelotas RS 96010‑560 Brazil. Graduate Program in Materials Science and Engineering Technological Development Center Federal University of Pelotas Pelotas RS 96010‑610 Brazil. Pelotas Dental School Graduate Program in Dentistry Federal University of Pelotas Pelotas RS 96010‑560 Brazil. rafael.lund@***. Graduate Program in Materials Science and Engineering Technological Development Center Federal University of Pelotas Pelotas RS 96010‑610 Brazil. rafael.lund@***.

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Giant Second-Order Nonlinearity and Anisotropy of Large-Sized Few-Layer SnS with Ferroelectric Stacking

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Advanced Optical materials 2024年第19期12卷

作者： Moqbel, Redhwan Nanae, Ryo Kitamura, Satsuki Lee, Ming-Hao Lan, Yann-Wen Lee, Chi-Cheng Nagashio, Kosuke Lin, Kung-Hsuan Department of Physics National Taiwan University No. 1 Sec. 4 Roosevelt Rd. Taipei106319 Taiwan Institute of Physics Academia Sinica No. 128 Sec. 2 Academia Rd. Nangang Dist. Taipei115201 Taiwan Nano-Science and Technology Program Taiwan International Graduate Program Academia Sinica No. 128 Sec. 2 Academia Rd. Nangang Dist. Taipei115201 Taiwan Department of Materials Engineering The University of Tokyo 7-3-1 Hongo Tokyo Bunkyo113-8656 Japan Center for Condensed Matter Sciences National Taiwan University Taipei10617 Taiwan The Key Consortium of Electron Microscopy National Taiwan University Taipei10617 Taiwan Department of Physics National Taiwan Normal University Taipei11677 Taiwan Department of Physics Tamkang University New Taipei Tamsui251301 Taiwan

The giant second-order nonlinearity of SnS with ferroelectric stacking is reported. Based on theoretical calculations, the susceptibility of second harmonic generation (SHG) from SnS with ferroelectric stacking is up to 1354 pm V−1, which is three orders of magnitude higher than the values of traditional nonlinear crystals such as BBO and KTP. The SHG from ferroelectric SnS few layers is experimentally measured and its intensity is found to be 131 times larger than that of a MoS2 monolayer under the same experimental conditions, with a photon energy of 1.55 eV. The SHG susceptibility is determined to be on the order of 100 pm V−1. Numerous SnS flakes are systematically investigated using polarization-resolved SHG. Micrometer-sized flakes with a single domain are found, and their SHG anisotropic patterns fit well with the theoretical calculations derived from first-principles methods. The variation in SHG anisotropic patterns, attributed to SHG interference from multiple domains, is investigated both theoretically and experimentally. Additionally, the impact of stacking disorder on the SHG anisotropic pattern is explored. It is demonstrated that polarization-resolved SHG microscopy is a valuable tool for identifying domains in SnS flakes and examining stacking disorder. © 2024 Wiley-VCH GmbH.

关键词： Harmonic generation

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Hexaazatriphenylene-Based Two-Dimensional Conductive Covalent Organic Framework with Anisotropic Charge Transfer

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Angewandte Chemie 2023年第42期135卷

作者： Seong-Wook Kim Hyeonjung Jung Dr. Mahmut Sait Okyay Dr. Hyuk-Jun Noh Sein Chung Young Hyun Kim Jong-Pil Jeon Prof. Dr. Bryan M. Wong Prof. Dr. Kilwon Cho Dr. Jeong-Min Seo Prof. Dr. Jung-Woo Yoo Prof. Dr. Jong-Beom Baek Department of Energy and Chemical Engineering/ Center for Dimension-Controllable Organic Frameworks Ulsan National Institute of Science and Technology (UNIST) Ulsan 44919 Republic of Korea These authors contributed equally to this work School of Materials Science and Engineering Ulsan National Institute of Science and Technology (UNIST) Ulsan 44919 Republic of Korea Materials Science & Engineering Program Department of Chemistry and Department of Physics & Astronomy University of California-Riverside Riverside CA 92521 USA Department of Chemistry Dartmouth College Hanover NH 03755 USA Department of Chemical Engineering Pohang University of Science and Technology Pohang 37673 Republic of Korea School of Materials Science and Engineering/ Graduate School of Semiconductor Materials and Devices Ulsan National Institute of Science and Technology (UNIST) Ulsan 44919 Republic of Korea

The development of covalent organic frameworks (COFs) with efficient charge transport is of immense interest for applications in optoelectronic devices. To enhance COF charge transport properties, electroactive building blocks and dopants can be used to induce extended conduction channels. However, understanding their intricate interplay remains challenging. We designed and synthesized a tailor-made COF structure with electroactive hexaazatriphenylene (HAT) core units and planar dioxin (D) linkages, denoted as HD-COF. With the support of theoretical calculations, we found that the HAT units in the HD-COF induce strong, eclipsed π–π stacking. The unique stacking of HAT units and the weak in-plane conjugation of dioxin linkages leads to efficient anisotropic charge transport. We fabricated HD-COF films to minimize the grain boundary effect of bulk COFs, which resulted in enhanced conductivity. As a result, the HD-COF films showed an electrical conductivity as high as 1.25 S cm −1 after doping with tris(4-bromophenyl)ammoniumyl hexachloroantimonate.

关键词： Anisotropic Charge Transfer Conductivity Covalent Organic Frameworks Doping

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