Journal of Physics: Materials最新文献

{"title":"Valleytronics in two-dimensional magnetic materials","authors":"Chaobo Luo, Zongyu Huang, H. Qiao, Xiang Qi, Xiangyang Peng","doi":"10.1088/2515-7639/ad3b6e","DOIUrl":"https://doi.org/10.1088/2515-7639/ad3b6e","url":null,"abstract":"\u0000 Valleytronics uses valleys to encode information. It combines other degrees of freedom to produce a more comprehensive, stable, and efficient information processing system. However, in nonmagnetic valleytronic materials, the valley polarization is transient and the depolarization occurs once the external excitation is withdrawn. Introduction of magnetic field is an effective approach to realizing the spontaneous valley polarization by breaking the time-reversal symmetry. In hexagonal magnetic valleytronic materials, the inequivalent valleys at the K and -K Dirac cones have asymmetric energy gaps and Berry curvatures. The time-reversal symmetry in nonmagnetic materials can be broken by applying an external magnetic field, adding a magnetic substrate or doping magnetic atoms. Recent theoretical studies have demonstrated that valleytronic materials with intrinsic ferromagnetism, now termed as ferrovalley materials, exhibit spontaneous valley polarization without the need for external fields to maintain the polarization. The coupling of the valley and spin degrees of freedom enables stable and unequal distribution of electrons in the two valleys and thus facilitating nonvolatile information storage. Hence, ferrovalley materials are promising materials for valleytronic devices. In this review, we first briefly overview valleytronics and its related properties, the ways to realize valley polarization in nonmagnetic valleytronic materials. Then we focus on the recent developments in two-dimensional ferrovalley materials, which can be classified according to their molecular formula and crystal structure: MX2; M(XY)2, M(XY2) and M(XYZ)2; M2X3, M3X8 and MNX6; MNX2Y2, M2X2Y6 and MNX2Y6; and the Janus structure ferrovalley materials. In the inequivalent valleys, the Berry curvatures have opposite signs with unequal absolute values, leading to anomalous valley Hall effect. When the valley polarization is large, the ferrovalleys can be selectively excited even with unpolarized light. Intrinsic valley polarization in two-dimensional ferrovalley materials is of great importance. It opens a new avenue for information-related applications and hence is under rapid development.","PeriodicalId":501825,"journal":{"name":"Journal of Physics: Materials","volume":"30 12","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140737850","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Impact of hydrogenation on the stability and mechanical properties of amorphous boron nitride","authors":"Onurcan Kaya, Luigi Colombo, Aleandro Antidormi, Marco A Villena, Mario Lanza, Ivan Cole, Stephan Roche","doi":"10.1088/2515-7639/ad367b","DOIUrl":"https://doi.org/10.1088/2515-7639/ad367b","url":null,"abstract":"Interconnect materials with ultralow dielectric constant, and good thermal and mechanical properties are crucial for the further miniaturization of electronic devices. Recently, it has been demonstrated that ultrathin amorphous boron nitride (aBN) films have a very low dielectric constant, high density (above 2.1 g cm⁻³), high thermal stability, and mechanical properties. The excellent properties of aBN derive from the nature and degree of disorder, which can be controlled at fabrication, allowing tuning of the physical properties for desired applications. Here, we report an improvement in the stability and mechanical properties of aBN upon hydrogen doping. With the introduction of a Gaussian approximation potential for atomistic simulations, we investigate the changing morphology of aBN with varying H doping concentrations. We found that for 8 at% of H doping, the concentration of <italic toggle=\"yes\">sp</italic>\u0000³-hybridized atoms reaches to a maximum which leads to an improvement of thermal stability and mechanical properties by 20%. These results will be a guideline for experimentalists and process engineers to tune the growth conditions of aBN films for numerous applications.","PeriodicalId":501825,"journal":{"name":"Journal of Physics: Materials","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140587578","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Topological stability of spin textures in Si/Co-doped helimagnet FeGe","authors":"Yao Guang, Yukako Fujishiro, Aito Tanaka, Licong Peng, Yoshio Kaneko, Naoya Kanazawa, Yoshinori Tokura, Xiuzhen Yu","doi":"10.1088/2515-7639/ad2ec4","DOIUrl":"https://doi.org/10.1088/2515-7639/ad2ec4","url":null,"abstract":"Element substitutions with magnetic or non-magnetic atoms are known to significantly impact the magnetic structure and related transport properties of magnets. To clarify the change of magnetic structure of B20-type magnets with element doping, we conduct real-space observations of spin textures and their temperature (<italic toggle=\"yes\">T</italic>)-magnetic field (<italic toggle=\"yes\">H</italic>) phase diagrams of a helimagnet FeGe with partially substituting Fe and Ge with Co and Si, respectively. The helical period (<italic toggle=\"yes\">λ</italic>) changes dramatically by the element doping: <italic toggle=\"yes\">λ</italic> increases by 147% to 103 nm in 30% Co-doped FeGe, whereas it decreases by around 70% to 49 nm in 30% Si-doped FeGe, compared to the <italic toggle=\"yes\">λ =</italic>70 nm in FeGe. Upon applying the magnetic field normally to (001), (110), and (111) thin plates of both FeSi_0.3Ge_0.7 and Fe_0.7Co_0.3Ge, the hexagonal skyrmion crystal (SkX) state emerges. The magnetic phase diagrams observed through the real-space imaging reveal that (1) the SkX can extend to a larger <italic toggle=\"yes\">T-H</italic> window by reducing the sample thickness or by cooling the sample under specific magnetic fields from temperatures above the transition temperature (<italic toggle=\"yes\">T_C\u0000</italic>); (2) the stability of the SkX phase differs between Si-doped and Co-doped FeGe: the SkX phase is most unstable in the (111) FeSi_0.3Ge_0.7, while it remains robust in the (111) Fe_0.7Co_0.3Ge. These differences indicate distinct anisotropic behavior in FeGe with magnetic (Co) and non-magnetic-element (Si) dopants.","PeriodicalId":501825,"journal":{"name":"Journal of Physics: Materials","volume":"100 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140316980","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Critical Review on the Application of Machine Learning in Supporting Auxetic Metamaterial Design","authors":"Chonghui Zhang, Y. Zhao","doi":"10.1088/2515-7639/ad33a4","DOIUrl":"https://doi.org/10.1088/2515-7639/ad33a4","url":null,"abstract":"\u0000 The progress of machine learning (ML) in the past years has opened up new opportunities to the design of auxetic metamaterials. However, successful implementation of ML algorithms remains challenging, particularly for complex problems such as domain performance prediction and inverse design. In this paper, we first reviewed classic auxetic designs and summarized their variants in different applications. The enormous variant design space leads to challenges using traditional design or topology optimization. Therefore, we also investigated how ML techniques can help address design challenges of auxetic metamaterials and when researchers should deploy them. The theories behind the techniques are explained, along with practical application examples from the analysed literature. The advantages and limitations of different ML algorithms are discussed and trends in the field are highlighted. Finally, two practical problems of ML-aided design, design scales and data collection are discussed.","PeriodicalId":501825,"journal":{"name":"Journal of Physics: Materials","volume":"11 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140247773","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High entropy ceramics for applications in extreme environments","authors":"T Z Ward, R P Wilkerson, B L Musicó, A Foley, M Brahlek, W J Weber, K E Sickafus, A R Mazza","doi":"10.1088/2515-7639/ad2ec5","DOIUrl":"https://doi.org/10.1088/2515-7639/ad2ec5","url":null,"abstract":"Compositionally complex materials have demonstrated extraordinary promise for structural robustness in extreme environments. Of these, the most commonly thought of are high entropy alloys, where chemical complexity grants uncommon combinations of hardness, ductility, and thermal resilience. In contrast to these metal–metal bonded systems, the addition of ionic and covalent bonding has led to the discovery of high entropy ceramics (HECs). These materials also possess outstanding structural, thermal, and chemical robustness but with a far greater variety of functional properties which enable access to continuously controllable magnetic, electronic, and optical phenomena. In this experimentally focused perspective, we outline the potential for HECs in functional applications under extreme environments, where intrinsic stability may provide a new path toward inherently hardened device design. Current works on high entropy carbides, actinide bearing ceramics, and high entropy oxides are reviewed in the areas of radiation, high temperature, and corrosion tolerance where the role of local disorder is shown to create pathways toward self-healing and structural robustness. In this context, new strategies for creating future electronic, magnetic, and optical devices to be operated in harsh environments are outlined.","PeriodicalId":501825,"journal":{"name":"Journal of Physics: Materials","volume":"72 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140317004","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Strain-induced magnetic anisotropy of multi-domain epitaxial EuPd2 thin films","authors":"Alfons G Schuck, Sebastian Kölsch, Adrian Valadkhani, Igor I Mazin, Roser Valentí, Michael Huth","doi":"10.1088/2515-7639/ad2d5e","DOIUrl":"https://doi.org/10.1088/2515-7639/ad2d5e","url":null,"abstract":"Europium intermetallic compounds show a variety of different ground states and anomalous physical properties due to the interactions between the localized 4f electrons and the delocalized electronic states. Europium is also the most reactive of the rare earth metals which might be the reason why very few works are concerned with the properties of Eu-based thin films. Here we address the low-temperature magnetic properties of ferromagnetic EuPd₂ thin films prepared by molecular beam epitaxy. The epitaxial (111)-oriented thin films grow on MgO (100) with eight different domain orientations. We analyze the low-temperature magnetic hysteresis behavior by means of micromagnetic simulations taking the multi-domain morphology explicitly into account and quantify the magnetic crystal anisotropy contribution. By <italic toggle=\"yes\">ab initio</italic> calculations we trace back the microscopic origin of the magnetic anisotropy to thin film-induced uniform biaxial strain.","PeriodicalId":501825,"journal":{"name":"Journal of Physics: Materials","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140311424","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Advance in twisted transition metal dichalcogenides: synthesis, characterization, and properties","authors":"Yueting Yang, Zhuojun Duan, Huimin Li, Song Liu","doi":"10.1088/2515-7639/ad2b7b","DOIUrl":"https://doi.org/10.1088/2515-7639/ad2b7b","url":null,"abstract":"The twist angle regulation strategy provides a feasible tool for studying the emerging properties of transition metal dichalcogenides (TMDCs). For the twisted TMDCs (t-TMDCs), there is the lattice mismatch and twist between layers, thus forming moiré superlattice. The formation of moiré superlattice brings about innovative properties to the t-TMDCs. These innovative properties have attracted more and more attention from researchers. This review firstly focuses on the synthesis methods of t-TMDCs, as well as the merits and shortcomings of each method. Secondly, the common spectral characterization and microscopic characterization methods are discussed. Thirdly, the prominent properties of t-TMDCs are briefly demonstrated, including ferroelectricity, flat band, and interlaminar excitons. Finally, we look forward to the potential application prospect and research direction of t-TMDCs.","PeriodicalId":501825,"journal":{"name":"Journal of Physics: Materials","volume":"33 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140311485","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Surface segregation in high-entropy alloys from alchemical machine learning","authors":"Arslan Mazitov, Maximilian A Springer, Nataliya Lopanitsyna, Guillaume Fraux, Sandip De, Michele Ceriotti","doi":"10.1088/2515-7639/ad2983","DOIUrl":"https://doi.org/10.1088/2515-7639/ad2983","url":null,"abstract":"High-entropy alloys (HEAs), containing several metallic elements in near-equimolar proportions, have long been of interest for their unique mechanical properties. More recently, they have emerged as a promising platform for the development of novel heterogeneous catalysts, because of the large design space, and the synergistic effects between their components. In this work we use a machine-learning potential that can model simultaneously up to 25 transition metals to study the tendency of different elements to segregate at the surface of a HEA. We use as a starting point a potential that was previously developed using exclusively crystalline bulk phases, and show that, thanks to the physically-inspired functional form of the model, adding a much smaller number of defective configurations makes it capable of describing surface phenomena. We then present several computational studies of surface segregation, including both a simulation of a 25-element alloy, that provides a rough estimate of the relative surface propensity of the various elements, and targeted studies of CoCrFeMnNi and IrFeCoNiCu, which provide further validation of the model, and insights to guide the modeling and design of alloys for heterogeneous catalysis.","PeriodicalId":501825,"journal":{"name":"Journal of Physics: Materials","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140311518","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Electronic conductivity in metal-graphene composites: the role of disordered carbon structures, defects, and impurities","authors":"K Nepal, C Ugwumadu, A Gautam, Keerti Kappagantula, D A Drabold","doi":"10.1088/2515-7639/ad261a","DOIUrl":"https://doi.org/10.1088/2515-7639/ad261a","url":null,"abstract":"This paper explores the transport properties of aluminum-carbon composite material via <italic toggle=\"yes\">ab initio</italic> methods. Interfacial and electronic dynamics of the aluminum-graphene interface structure were investigated using models of amorphous graphene added to an aluminum matrix. We examine the impact on electronic conduction caused by the presence of nitrogen impurities within the interfacial amorphous graphene layer. We elucidate the conduction mechanisms by using a projection of the electronic conductivity into space.","PeriodicalId":501825,"journal":{"name":"Journal of Physics: Materials","volume":"4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140010680","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Exciton-carrier coupling in a metal halide perovskite nanocrystal assembly probed by two-dimensional coherent spectroscopy","authors":"Esteban Rojas-Gatjens, David Otto Tiede, Katherine A Koch, Carlos Romero-Perez, Juan F Galisteo-López, Mauricio E Calvo, Hernán Míguez, Ajay Ram Srimath Kandada","doi":"10.1088/2515-7639/ad229a","DOIUrl":"https://doi.org/10.1088/2515-7639/ad229a","url":null,"abstract":"The surface chemistry and inter-connectivity within perovskite nanocrystals play a critical role in determining the electronic interactions. They manifest in the Coulomb screening of electron–hole correlations and the carrier relaxation dynamics, among other many-body processes. Here, we characterize the coupling between the exciton and free carrier states close to the band-edge in a ligand-free formamidinium lead bromide nanocrystal assembly via two-dimensional coherent spectroscopy. The optical signatures observed in this work show: (i) a nonlinear spectral lineshape reminiscent of Fano-like interference that evidences the coupling between discrete electronic states and a continuum, (ii) symmetric excited state absorption cross-peaks that suggest the existence of a coupled exciton-carrier excited state, and (iii) ultrafast carrier thermalization and exciton formation. Our results highlight the presence of coherent coupling between exciton and free carriers, particularly in the sub-100 femtosecond timescales.","PeriodicalId":501825,"journal":{"name":"Journal of Physics: Materials","volume":"33 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139770107","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}