Physical Review Materials最新文献

{"title":"Superconducting phase diagram in BixNi1–x thin films: The effects of Bi stoichiometry on superconductivity","authors":"Jihun Park, Jarryd A. Horn, Dylan J. Kirsch, Rohit K. Pant, Hyeok Yoon, Sungha Baek, Suchismita Sarker, Apurva Mehta, Xiaohang Zhang, Seunghun Lee, Richard Greene, Johnpierre Paglione, Ichiro Takeuchi","doi":"10.1103/physrevmaterials.8.074805","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.074805","url":null,"abstract":"The Bi-Ni binary system has been of interest due to possible unconventional superconductivity aroused therein, such as time-reversal symmetry breaking in Bi/Ni bilayers or the coexistence of superconductivity and ferromagnetism in <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Bi</mi><mn>3</mn></msub><mi>Ni</mi></mrow></math> crystals. While Ni acts as a ferromagnetic element in such systems, the role of the strong spin-orbit coupling element Bi in superconductivity has remained unexplored. In this work, we systematically studied the effects of Bi stoichiometry on the superconductivity of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Bi</mi><mi>x</mi></msub><msub><mi>Ni</mi><mrow><mn>1</mn><mo>–</mo><mi>x</mi></mrow></msub></mrow></math> thin films (<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>x</mi><mo>≈</mo><mn>0.5</mn><mo>–</mo><mn>0.9</mn></mrow></math>) fabricated via a composition-spread approach. The superconducting phase map of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Bi</mi><mi>x</mi></msub><msub><mi>Ni</mi><mrow><mn>1</mn><mo>–</mo><mi>x</mi></mrow></msub></mrow></math> thin films exhibited a superconducting composition region attributable to the intermetallic <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Bi</mi><mn>3</mn></msub><mi>Ni</mi></mrow></math> phase with different amounts of excess Bi, revealed by synchrotron x-ray diffraction analysis. Interestingly, the mixed-phase region with <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Bi</mi><mn>3</mn></msub><mi>Ni</mi></mrow></math> and Bi showed unusual increases in the superconducting transition temperature and residual resistance ratio as more Bi impurities were included, with the maximum <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>T</mi><mi mathvariant=\"normal\">c</mi></msub></math> (<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mo>=</mo><mn>4.2</mn><mspace width=\"0.28em\"></mspace><mi mathvariant=\"normal\">K</mi></mrow></math>) observed at <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>x</mi><mo>≈</mo><mn>0.79</mn></mrow></math>. A correlation analysis of structural, electrical, and magneto-transport characteristics across the composition variation revealed that the unusual superconducting “dome” is due to two competing roles of Bi: impurity scattering and carrier doping. We found that the carrier doping effect is dominant in the mild doping regime <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mo>(</mo><mn>0.74</mn><mo>≤</mo><mi>x</mi><mo>≤</mo><mn>0.79</mn><mo>)</mo></mrow></math>, while impurity scattering becomes more pronounced at larger Bi stoichiometry.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141783157","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cation disorder in MgSnN2 and its effects on the electronic properties","authors":"Jing Huang, Jun Kang","doi":"10.1103/physrevmaterials.8.074604","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.074604","url":null,"abstract":"Ternary nitride <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>MgSnN</mi><mn>2</mn></msub></math> is a promising candidate to fill the “green gap” of nitride-based light-emitting diodes. The coexistence of two different valence cations offers a unique tunability on its electronic properties through controlling the degree of cation site ordering without a concomitant change in stoichiometry. In this work, the structural and electronic properties of cation-disordered <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>MgSnN</mi><mn>2</mn></msub></math> are studied through a combination of density functional theory calculations, cluster expansion, and Monte Carlo simulations. The order-disorder phase transition is analyzed, and the short-range and long-range order parameters quantifying the degree of disorder are calculated. A strong correlation between the two parameters is observed, indicating the absence of the octet-rule-conserving disorder. Cation disorder has two main effects on the electronic properties of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>MgSnN</mi><mn>2</mn></msub></math>. One is the reduction of the band gap, and the other is the strong localization of valence band edge states. Further analysis showed that the localization is a consequence of the weak interatomic coupling between the N atoms and the disorder-induced fluctuation of the local electrostatic potentials on the N atoms. These results could be helpful for the understanding of disorder effects in <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>MgSnN</mi><mn>2</mn></msub></math>, as well as the tuning of its properties through the control of cation ordering.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141783158","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Challenges in extracting nonlinear current-induced phenomena in Ca2RuO4","authors":"Giordano Mattoni, Kazumi Fukushima, Shingo Yonezawa, Fumihiko Nakamura, Yoshiteru Maeno","doi":"10.1103/physrevmaterials.8.074411","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.074411","url":null,"abstract":"An appealing direction to change the properties of strongly correlated materials is to induce nonequilibrium steady states by the application of a direct current. While access to these novel states is of high scientific interest, Joule heating due to current flow often constitutes a hurdle to identify nonthermal effects. The biggest challenge usually resides in measuring accurately the temperature of a sample subjected to direct current, and to use probes that give direct information of the material. In this work, we exploit the simultaneous measurement of electrical transport and magnetization to probe nonequilibrium steady states in <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Ca</mi><mn>2</mn></msub><mi>Ru</mi><msub><mi mathvariant=\"normal\">O</mi><mn>4</mn></msub></mrow></math>. In order to reveal nonthermal current-induced effects, we employ a simple model of Joule self-heating to remove the effects of heating and discuss the importance of temperature inhomogeneity within the sample. Our approach provides a solid basis for investigating current-induced phenomena in highly resistive materials.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141783156","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of local chain stiffness on oligomer crystallization from a melt","authors":"Pierre Kawak, Christopher Akiki, Douglas R. Tree","doi":"10.1103/physrevmaterials.8.075606","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.075606","url":null,"abstract":"While the process by which a polymer crystal nucleates from the melt has been extensively studied via molecular simulation, differences in polymer models and simulated crystallization conditions have led to seemingly contradictory results. We make steps to resolve this controversy by computing low-temperature phase diagrams of oligomer melts using Wang-Landau Monte Carlo simulations. Two qualitatively different crystallization mechanisms are possible depending on the local bending stiffness potential. Polymers with a discrete bending potential crystallize via a single-step mechanism, whereas polymers with a continuous bending potential can crystallize via a two-step mechanism that includes an intermediate nematic phase. Other model differences can be quantitatively accounted for using an effective volume fraction and a temperature scaled by the bending stiffness. These results suggest that at least two universality classes of nucleation exist for melts and that local chain stiffness is a key determining factor in the mechanism of nucleation.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141754128","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Probing intrinsic magnetization dynamics of the Y3Fe5O12/Bi2Te3 interface at low temperature","authors":"A. R. Will-Cole, Valeria Lauter, Alexander Grutter, Carsten Dubs, David A. Lidsky, Morris Lindner, Timmy Reimann, Nirjhar Bhattacharjee, Tzu-Ming Lu, Peter Sharma, Nichole R. Valdez, Charles J. Pearce, Todd C. Monson, Matthew Matzelle, Arun Bansil, Don Heiman, Nian X. Sun","doi":"10.1103/physrevmaterials.8.074409","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.074409","url":null,"abstract":"Topological insulator–magnetic insulator (TI–MI) heterostructures hold significant promise in the field of spintronics, offering the potential for manipulating magnetization through topological surface state–enabled spin-orbit torque. However, many TI–MI interfaces are plagued by issues such as contamination within the magnetic insulator layer and the presence of a low-density transitional region of the topological insulator. These interfacial challenges often obscure the intrinsic behavior of the TI–MI system. In this study, we addressed these challenges by depositing sputtered <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Bi</mi><mn>2</mn></msub><msub><mi>Te</mi><mn>3</mn></msub></mrow></math> on liquid phase epitaxy grown <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi mathvariant=\"normal\">Y</mi><mn>3</mn></msub><msub><mi>Fe</mi><mn>5</mn></msub><msub><mi mathvariant=\"normal\">O</mi><mn>12</mn></msub><mo>/</mo><msub><mi>Gd</mi><mn>3</mn></msub><msub><mi>Ga</mi><mn>5</mn></msub><msub><mi mathvariant=\"normal\">O</mi><mn>12</mn></msub></mrow></math>. The liquid phase epitaxy grown <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi mathvariant=\"normal\">Y</mi><mn>3</mn></msub><msub><mi>Fe</mi><mn>5</mn></msub><msub><mi mathvariant=\"normal\">O</mi><mn>12</mn></msub></mrow></math> has been previously shown to have exceptional interface quality, without an extended transient layer derived from interdiffusion processes of the substrate or impurity ions, thereby eliminating rare-earth impurity-related losses in the MI at low temperatures. At the TI–MI interface, high-resolution depth-sensitive polarized neutron reflectometry confirmed the absence of a low-density transitional growth region of the TI. By overcoming these undesirable interfacial effects, we isolate and probe the intrinsic low-temperature magnetization dynamics and transport properties of the TI–MI interface. Our findings revealed strong spin pumping at low temperatures, accompanied by an additional in-plane anisotropy. The enhanced spin pumping at low temperatures is correlated with the observed suppression of bulk conduction and the weak antilocalization in the TI film, highlighting the interplay between the transport and spin pumping behavior in the TI–MI system.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141754124","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Nodal line induced large transverse thermoelectric response in the D03-type Heusler compound Fe3Si","authors":"Susumu Minami, Sota Hogaki, Takahiro Shimada","doi":"10.1103/physrevmaterials.8.075403","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.075403","url":null,"abstract":"Giant magnetic transverse thermoelectric effect, anomalous Nernst effect (ANE), was theoretically and experimentally observed in <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>3</mn><mi>d</mi></mrow></math>-transition metal compounds. The intrinsic components of ANE can be described from the electronic structure based on the Berry phase concept. The topological electronic structure, such as the Weyl node and nodal lines, induces large Berry curvature, one origin of giant ANE. We investigated transverse thermoelectric properties on ferromagnetic <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi mathvariant=\"normal\">D</mi><msub><mn>0</mn><mn>3</mn></msub></mrow></math>-type Heusler compounds <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Fe</mi><mn>3</mn></msub><mi>Si</mi></mrow></math> based on first-principles calculations. We found large transverse thermoelectric conductivity <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>α</mi><mrow><mi>x</mi><mi>y</mi></mrow></msub><mo>∼</mo><mn>5</mn><mspace width=\"4pt\"></mspace><msup><mrow><mi>AK</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup><msup><mrow><mi mathvariant=\"normal\">m</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math> is realized with hole carrier doping at room temperature. We also clarified that the nodal line and its stationary point enhance transverse thermoelectric conductivity. These results give us a clue to design high-performance ANE-based magnetic thermoelectric materials.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141754096","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Proximate Tomonaga-Luttinger liquid in a spin-1/2 ferromagnetic XXZ chain compound","authors":"Boqiang Li, Xun Chen, Yuqian Zhao, Zhaohua Ma, Zongtang Wan, Yuesheng Li","doi":"10.1103/physrevmaterials.8.074410","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.074410","url":null,"abstract":"The spin-<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>1</mn><mo>/</mo><mn>2</mn></mrow></math> ferromagnetic XXZ chain is a prototypical many-body quantum model, exactly solvable via the integrable Bethe ansatz method, hosting a Tomonaga-Luttinger spin liquid. However, its clear experimental realizations remain absent. Here, we present a thorough investigation of the magnetism of the structurally disorder-free compound <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>LuCu</mi><msub><mrow><mo>(</mo><mi>OH</mi><mo>)</mo></mrow><mn>3</mn></msub><msub><mi>SO</mi><mn>4</mn></msub></mrow></math>. By conducting magnetization and electron-spin-resonance measurements on the single-crystal sample, we establish that the title compound approximates the spin-<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>1</mn><mo>/</mo><mn>2</mn></mrow></math> ferromagnetic XXZ chain model with a nearest-neighbor exchange strength of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>J</mi><mn>1</mn></msub><mo>∼</mo><mn>65</mn><mspace width=\"0.16em\"></mspace><mi mathvariant=\"normal\">K</mi></mrow></math> and an easy-plane anisotropy of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mo>∼</mo><mn>0.994</mn></mrow></math>. The specific heat demonstrates a distinctive power-law behavior at low magnetic fields (with energy scales <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mo>≤</mo><mn>0.02</mn><msub><mi>J</mi><mn>1</mn></msub></mrow></math>) and low temperatures <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mo>(</mo><mi>T</mi><mo>≤</mo><mn>0.03</mn><msub><mi>J</mi><mn>1</mn></msub><mo>)</mo></mrow></math>. This behavior is consistent with the expectations of the ideal spin-<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>1</mn><mo>/</mo><mn>2</mn></mrow></math> ferromagnetic XXZ chain model, thereby supporting the formation of a gapless Tomonaga-Luttinger spin liquid in <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>LuCu</mi><msub><mrow><mo>(</mo><mi>OH</mi><mo>)</mo></mrow><mn>3</mn></msub><msub><mi>SO</mi><mn>4</mn></msub></mrow></math>.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141754127","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Possible Wigner states in CrI3 heterostructures with graphene: A tight-binding model perspective","authors":"Igor Rozhansky, Vladimir Fal'ko","doi":"10.1103/physrevmaterials.8.074007","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.074007","url":null,"abstract":"In this study, we present an effective tight-binding model for an accurate description of the lowest energy quadruplet of a conduction band in a ferromagnetic <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>Cr</mi><msub><mi>X</mi><mn>3</mn></msub></mrow></math> monolayer, tuned to the complementary <i>ab initio</i> density functional theory simulations. This model, based on a minimum number of chromium orbitals, captures a distinctively flat dispersion in those bands but requires taking into account hoppings beyond nearest neighbors, revealing ligand-mediated electron pathways connecting remote chromium sites. Doping of states in the lowest conduction band of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>Cr</mi><msub><mi>X</mi><mn>3</mn></msub></mrow></math> requires charge transfer, which, according to recent studies [Tenasini <i>et al.</i>, <span>Nano Lett.</span> <b>22</b>, 6760 (2022); Tseng <i>et al.</i>, <span>Nano Lett.</span> <b>22</b>, 8495 (2022); Cardoso <i>et al.</i>, <span>Phys. Rev. B</span> <b>108</b>, 184423 (2023)], can occur in <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mrow><mi>graphene</mi><mo>(</mo><mi mathvariant=\"normal\">G</mi><mo>)</mo></mrow><mo>/</mo><mi>Cr</mi><msub><mi>X</mi><mn>3</mn></msub></mrow></math> heterostructures. Here, we use the detailed description of the lowest conduction band in <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>CrI</mi><mn>3</mn></msub></math> to show that <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi mathvariant=\"normal\">G</mi><mo>/</mo><msub><mi>CrI</mi><mn>3</mn></msub><mo>/</mo><mi mathvariant=\"normal\">G</mi></mrow></math> and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi mathvariant=\"normal\">G</mi><mo>/</mo><msub><mi>CrI</mi><mn>3</mn></msub></mrow></math> are type-II heterostructures where light holes in graphene would coexist with heavy electrons in the magnetic layer, where the latter can be characterized by Wigner-Seitz radius <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>r</mi><mi>s</mi></msub><mo>∼</mo><mn>25</mn><mo>−</mo><mn>35</mn></mrow></math> (as estimated for hBN-encapsulated structures).","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141754122","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Probing the interface and individual layers in cuprate/manganite heterostructures by Raman spectroscopy","authors":"F. Lyzwa, A. Chan, K. Fürsich, B. Keimer, C. Faugeras, Yu. G. Pashkevich, C. Bernhard, M. Minola, B. P. P. Mallett","doi":"10.1103/physrevmaterials.8.074804","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.074804","url":null,"abstract":"We report a comprehensive set of polarized Raman spectra on thin-film multilayers of the high-<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>T</mi><mi>c</mi></msub></math> superconductor <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mrow><mi>YBa</mi></mrow><mn>2</mn></msub><msub><mrow><mi>Cu</mi></mrow><mn>3</mn></msub><msub><mrow><mi mathvariant=\"normal\">O</mi></mrow><mn>7</mn></msub></math> and electrically insulating manganites <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>R</mi><msub><mi>MnO</mi><mn>3</mn></msub></mrow></math> (<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>R</mi><mo>=</mo></mrow></math> rare-earth partially substituted with group-II elements) hosting magnetic, charge and orbital order (COO). Such multilayers have been shown to exhibit a unique insulating-to-superconducting transition that is induced by magnetic field, electric field, or by tailoring the chemical composition of the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>R</mi></math> site of the manganite. The Raman spectra show significant Jahn-Teller distortions of the manganite structure, which correlate with COO, approximately 90 K above the magnetic ordering temperature of 140 K. Based on the Raman data and earlier electrical transport studies of single-layer manganite films, we argue that the manganite layers in our heterostructures remain electrically insulating across the range of investigated temperatures, dopings, and magnetic fields. The Raman spectra show a pronounced redshift and broadening of lattice vibrations around 200 <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mrow><mi>cm</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></math> in the multilayers compared to those of manganite films, which may indicate hybridization with <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mrow><mi>YBa</mi></mrow><mn>2</mn></msub><msub><mrow><mi>Cu</mi></mrow><mn>3</mn></msub><msub><mrow><mi mathvariant=\"normal\">O</mi></mrow><mn>7</mn></msub></math> phonons. We also observe additional excitations at 690 <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mrow><mi>cm</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></math> and 830 <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mrow><mi>cm</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></math> that are absent in the single films or bulk responses, which we discuss to originate from the cuprate/manganite interface. These observations demonstrate that the phonon spectrum is significantly modified in our multilayer samples. This is expected to play an important role in the mechanism of the insulating-to-superconducting transition found in these cuprate-manganite multilayers.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141743325","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tetragonal phases in Fe-Ga alloys: A quantitative study","authors":"A. M. Balagurov, I. A. Bobrikov, D. Yu. Chernyshov, A. S. Sohatsky, S. V. Sumnikov, B. Yerzhanov, I. S. Golovin","doi":"10.1103/physrevmaterials.8.073604","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.073604","url":null,"abstract":"Currently, the dominant model for the formation of enhanced magnetostriction of Fe-Ga alloys is based on the assumption of the presence of microscopic inclusions with a tetragonal <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>L</mi><msub><mn>6</mn><mn>0</mn></msub></mrow></math> structure in the cubic matrix of the alloy. However, no evidence for the presence of this phase in the bulk of the alloys in amounts sufficient to have a noticeable effect on the magnitude of magnetostriction has been obtained so far. To test this hypothesis, a detailed scanning of the reciprocal space of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi mathvariant=\"normal\">F</mi><msub><mi mathvariant=\"normal\">e</mi><mn>81</mn></msub><mi mathvariant=\"normal\">G</mi><msub><mi mathvariant=\"normal\">a</mi><mn>19</mn></msub><mi mathvariant=\"normal\">T</mi><msub><mi mathvariant=\"normal\">b</mi><mrow><mn>0.1</mn></mrow></msub></mrow></math> and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Fe</mi><mn>73</mn></msub><msub><mi>Ga</mi><mn>27</mn></msub></mrow></math> single crystals was carried out at ESRF at high photon flux stations. In particular, it was possible to reliably record superstructure diffraction peaks, the intensity of which was at a level of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>2</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>6</mn></mrow></msup></mrow></math> from the intensity of the fundamental peaks. Nevertheless, neither the presence of superstructure diffraction peaks obviously belonging to the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>L</mi><msub><mn>6</mn><mn>0</mn></msub></mrow></math> phase nor the tetragonal splitting of the fundamental diffraction peaks into components, which could indicate the presence of this phase in the samples, was detected. Similar results were obtained using complementary methods (electron and neutron diffraction). Based on the performed analysis of the background level in the places of the expected positions of superstructure peaks of the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>L</mi><msub><mn>6</mn><mn>0</mn></msub></mrow></math> phase, it was found that the volume fraction of this phase in the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi mathvariant=\"normal\">F</mi><msub><mi mathvariant=\"normal\">e</mi><mn>81</mn></msub><mi mathvariant=\"normal\">G</mi><msub><mi mathvariant=\"normal\">a</mi><mn>19</mn></msub><mi mathvariant=\"normal\">T</mi><msub><mi mathvariant=\"normal\">b</mi><mrow><mn>0.1</mn></mrow></msub></mrow></math> alloy cannot exceed 0.2 %. The presence of a previously discovered <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>X</mi></math> phase with hexagonal or orthorhombic symmetry in a crystal with 27 at. % Ga was confirmed.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141743108","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}