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1.
In the present work, we provide a comprehensive numerical investigation of the magnetic properties and phase spectra of three types of spin-1/2 branched chains consisting of one, two and three side spins per unit block with intra-chain interaction and a uniform inter-chain interaction in the presence of an external magnetic field. In a specific magnetic field interval, the low-temperature magnetization of these chains shows a step-like behavior with a pronounced plateau depending on the strength and the type of intra-chain interaction being ferromagnetic or antiferromagnetic. We demonstrate that when inter-chain interaction is antiferromagnetic and intra-chain interaction is ferromagnetic, the magnetization of the models manifests a smooth increase without a plateau, which is evidence of the existence of a Luttinger-like spin liquid phase before reaching its saturation value. On the other hand, when is ferromagnetic and is antiferromagnetic, the low-temperature magnetization of the chain with two branches shows an intermediate plateau at one-half of the saturation magnetization that breaks a quantum spin liquid phase into two regions. The magnetization of the chain with three branches exhibits two intermediate plateaus and two regions of a quantum spin liquid. We demonstrate that the chains with more than one side spin illustrate in their ground-state phase diagram a Kosterlitz–Thouless transition from a gapful phase to a gapless spin liquid phase. 相似文献
2.
We report synthesis, crystal structure, and physical properties of Sr Cr AsO . The new compound crystallizes in a Sr GaO CuS-type structure with two distinct Cr sites, Cr(1) in the perovskite-like block layers of “Sr Cr O ” and Cr(2) in the ThCr Si -type layers of “SrCr As ”. An inter-block-layer charge transfer is explicitly evidenced, which dopes electrons in the CrO planes and simultaneously dopes holes into the CrAs layers. Measurements of electrical resistivity, magnetization, and specific heat, in combination with density-functional theoretical calculations, indicate that the title material is an antiferromagnetic metal. The Cr(2) magnetic moments in the CrAs layers order at 420 K, while the Cr(1) spins in the CrO planes show quasi-two-dimensional magnetism with long-range ordering below 80 K. Both Néel temperatures are significantly reduced, compared with those of the cousin material Sr Cr As O , probably due to the intrinsic charge-carrier doping. Complex re-entrant magnetic transitions with a huge magnetic hysteresis were observed at low temperatures. 相似文献
3.
To go deep into the origin of MgCl supported Ziegler-Natta catalysis we need to fully understand the structure and properties of precatalytic nanoclusters MgCl/TiCl in presence of Lewis bases as internal donors (ID). In this work MgCl/TiCl nanoplatelets derived by machine learning and DFT calculations have been used to model the interaction with ethyl-benzoate EB as ID, with available exposed sites of binary TiCl/MgCl systems. The influence of vicinal TiCl and coadsorbed TiCl on energetic, structural and spectroscopic behaviour of EB has been considered. The adsorption of homogeneous-like TiClEB and TiCl(EB) at the various surface sites have been also simulated. B3LYP-D2 and M06 functionals combined with TZVP quality basis set have been adopted for calculations. The adducts have been characterized by computing IR and Raman spectra that have been found to provide specific fingerprints useful to identify surface species; IR spectra have been successfully compared to available experimental data. 相似文献
4.
Understanding the coupling between electrons and phonons in iron chalcogenides FeTeSe has remained a critical but arduous project in recent decades. The direct observation of the electron–phonon coupling effect through electron dynamics and vibrational properties has been lacking. Here, we report the first pressure-dependent ultrafast photocarrier dynamics and Raman scattering studies on an iron chalcogenide FeTeSe to explore the interaction between electrons and phonons in this unconventional superconductor. The lifetime of the excited electrons evidently decreases as the pressure increases from 0 to 2.2 GPa, and then increases with further compression. The vibrational properties of the phonon mode exhibit similar behavior, with a pronounced frequency reduction appearing at approximately 2.3 GPa. The dual evidence reveals the enhanced electron–phonon coupling strength with pressure in FeTeSe. Our results give an insight into the role of the electron–phonon coupling effect in iron-based superconductors. 相似文献
5.
Evaporation kinetics of tramp elements (M = As and Sn) in liquid iron were investigated by high-temperature gas–liquid reaction experiments and a phenomenological kinetic model. Residual content of As or Sn in the liquid iron ([pct M]) during the evaporation was measured in the temperature range of 1680 C to 1760 C. [pct As] and [pct Sn] decreased faster as the reaction temperature and [pct C] increased. Assuming first-order reaction kinetics, the apparent rate constants () were obtained at each reaction temperature and [pct C]. [pct M] in a liquid iron during the top-blown oxygen steelmaking process was simulated, with an emphasis on enlarging the reaction surface area by forming a large number of liquid iron droplets. The surface area and the droplet generation rate were obtained based on the oxygen-blowing condition. The whole surface area increased up to ∼163 times the initial liquid iron (bath) surface area, due to the generation of the droplets. Using the obtained in the present study, the evaporation of M during the top-blown oxygen steelmaking process for 200 tonnes of liquid iron was simulated. For a condition of [pct M] = 0.005 (M = As and Sn), As and Sn could be removed from the liquid iron, which was seen to be much improved by the consideration of the droplet generation. However, additional actions are required to improve the evaporation rate, as the evaporation rate in the BOF process was not fast enough to be practically considered. 相似文献
6.
Melissa E. Henderson James Beare Sudarshan Sharma Markus Bleuel Pat Clancy David G. Cory Michael G. Huber Casey A. Marjerrison Mathew Pula Dusan Sarenac Evan M. Smith Kirill Zhernenkov Graeme M. Luke Dmitry A. Pushin 《Materials》2021,14(16)
Topologically nontrivial spin textures host great promise for future spintronic applications. Skyrmions in particular are of burgeoning interest owing to their nanometric size, topological protection, and high mobility via ultra-low current densities. It has been previously reported through magnetic susceptibility, microscopy, and scattering techniques that CoZnMn forms an above room temperature triangular skyrmion lattice. Here, we report the synthesis procedure and characterization of a polycrystalline CoZnMn disordered bulk sample. We employ powder X-ray diffraction and backscatter Laue diffraction as characterization tools of the crystallinity of the samples, while magnetic susceptibility and Small Angle Neutron Scattering (SANS) measurements are performed to study the skyrmion phase. Magnetic susceptibility measurements show a dip anomaly in the magnetization curves, which persists over a range of approximately 305 K–315 K. SANS measurements reveal a rotationally disordered polydomain skyrmion lattice. Applying a symmetry-breaking magnetic field sequence, we were able to orient and order the previously jammed state to yield the prototypical hexagonal diffraction patterns with secondary diffraction rings. This emergence of the skyrmion order serves as a unique demonstration of the fundamental interplay of structural disorder and anisotropy in stabilizing the thermal equilibrium phase. 相似文献
7.
Strain Effects on the Electronic and Thermoelectric Properties of n(PbTe)-m(Bi2Te3) System Compounds
Owing to their low lattice thermal conductivity, many compounds of the n(PbTe)-m(BiTe) homologous series have been reported in the literature with thermoelectric (TE) properties that still need improvement. For this purpose, in this work, we have implemented the band engineering approach by applying biaxial tensile and compressive strains using the density functional theory (DFT) on various compounds of this series, namely BiTe, PbBiTe, PbBiTe and PbBiTe. All the fully relaxed BiTe, PbBiTe, PbBiTe and PbBiTe compounds are narrow band-gap semiconductors. When applying strains, a semiconductor-to-metal transition occurs for all the compounds. Within the range of open-gap, the electrical conductivity decreases as the compressive strain increases. We also found that compressive strains cause larger Seebeck coefficients than tensile ones, with the maximum Seebeck coefficient being located at −2%, −6%, −3% and 0% strain for p-type BiTe, PbBiTe, PbBiTe and PbBiTe, respectively. The use of the quantum theory of atoms in molecules (QTAIM) as a complementary tool has shown that the van der Waals interactions located between the structure slabs evolve with strains as well as the topological properties of BiTe and PbBiTe. This study shows that the TE performance of the n(PbTe)-m(BiTe) compounds is modified under strains. 相似文献
8.
Electronic structure and magnetic properties of FeSe are calculated using the density functional approach. Due to the metallic properties, magnetic moments of the iron atoms in two nonequivalent positions in the unit cell are different from ionic values for Fe and Fe and are equal to and , making the system ferrimagnetic. The total magnetic moment for the unit cell is . Under isotropic compression, the total magnetic moment decreases non-monotonically and correlates with the non-monotonic dependence of the density of states at the Fermi level . For 7% compression, the magnetic order changes from the ferrimagnetic to the ferromagnetic. At 14% compression, the magnetic order disappears and the total magnetic moment becomes zero, leaving the system in a paramagnetic state. This compression corresponds to the pressure of 114 GPa. The magnetic ordering changes faster upon application of an isotropic external pressure due to the sizeable anisotropy of the chemical bondings in FeSe. The ferrimagnetic and paramagnetic states occur under pressures of 5.0 and 8.0 GPa, respectively. The system remains in the metallic state for all values of compression. 相似文献
9.
Two-dimensional (2D) materials have potential applications in nanoscale sensors and spintronic devices. Herein, motivated by experimental synthesis of a CrI monolayer possessing intrinsic magnetism and a Janus MoSSe monolayer with piezoelectricity, we propose a 2D Janus CrIF monolayer as a multifunctional material exhibiting both piezoelectricity and ferromagnetism. Using density functional theory calculations, we systematically investigated the structural stability and the electronic, magnetic, and piezoelectric properties of the Janus CrIF monolayer. We predicted that a vertical polarization of up to −0.155 × 10 C/m is induced in the CrIF monolayer due to the breaking of symmetry. The origination mechanism of polarization was demonstrated in terms of a local dipole moment calculated by maximally localized Wannier functions. Meanwhile, it was found that a remarkable piezoelectric response can be produced under a uniaxial strain in the basal plane. The calculated piezoelectric coefficients of the CrIF monolayer compare favorably with those of the frequently used bulk piezoelectric materials such as –quartz and wurtzite AlN. Particularly, the e and d values of the CrIF monolayer are nearly 10 times as large as that of Mo-based transition metal dichalcogenides. We also found that the magnitude of e mainly arises from the ionic contribution, while the electronic contribution can be nearly neglected. The considerable piezoelectric response combined with the intrinsic magnetism make the Janus CrIF monolayer a potential candidate for novel multifunctional devices integrating both piezoelectric and spintronic applications. 相似文献
10.
Brian Walls Oisín Murtagh Sergey I. Bozhko Andrei Ionov Andrey A. Mazilkin Daragh Mullarkey Ainur Zhussupbekova Dmitry A. Shulyatev Kuanysh Zhussupbekov Nikolai Andreev Nataliya Tabachkova Igor V. Shvets 《Materials》2022,15(21)
The strongly correlated electron material, vanadium dioxide (VO), has seen considerable attention and research application in metal-oxide electronics due to its metal-to-insulator transition close to room temperature. Vacuum annealing a VO(010) single crystal results in Wadsley phases (VO, n > 1) and VO. The resistance changes by a factor of 20 at 342 K, corresponding to the metal-to-insulator phase transition of VO. Macroscopic voltage-current measurements with a probe separation on the millimetre scale result in Joule heating-induced resistive switching at extremely low voltages of under a volt. This can reduce the hysteresis and facilitate low temperature operation of VO devices, of potential benefit for switching speed and device stability. This is correlated to the low resistance of the system at temperatures below the transition. High-resolution transmission electron microscopy measurements reveal a complex structural relationship between VO, VO and VO crystallites. Percolation paths incorporating both VO and metallic VO are revealed, which can reduce the resistance below the transition and result in exceptionally low voltage resistive switching. 相似文献
11.
Jannis Thien Jascha Bahlmann Andreas Alexander Kevin Ruwisch Jari Rodewald Tobias Pohlmann Martin Hoppe Fatih Alarslan Martin Steinhart Baki Altuncevahir Padraic Shafer Carola Meyer Florian Bertram Joachim Wollschlger Karsten Küpper 《Materials》2022,15(1)
Here, we present the (element-specific) magnetic properties and cation ordering for ultrathin Co-rich cobalt ferrite films. Two Co-rich films with different stoichiometry ( and ) have been formed by reactive solid phase epitaxy due to post-deposition annealing from epitaxial CoO/FeO bilayers deposited before on Nb-doped SrTiO(001). The electronic structure, stoichiometry and homogeneity of the cation distribution of the resulting cobalt ferrite films were verified by angle-resolved hard X-ray photoelectron spectroscopy. From X-ray magnetic circular dichroism measurements, the occupancies of the different sublattices were determined using charge-transfer multiplet calculations. For both ferrite films, a partially inverse spinel structure is found with increased amount of cations in the low-spin state on octahedral sites for the film. These findings concur with the results obtained by superconducting quantum interference device measurements. Further, the latter measurements revealed the presence of an additional soft magnetic phase probably due to cobalt ferrite islands emerging from the surface, as suggested by atomic force microscope measurements. 相似文献
12.
Vasily R. Shaginyan Alfred Z. Msezane George S. Japaridze Stanislav A. Artamonov Yulya S. Leevik 《Materials》2022,15(11)
This review considers the topological fermion condensation quantum phase transition (FCQPT) that explains the complex behavior of strongly correlated Fermi systems, such as frustrated insulators with quantum spin liquid and heavy fermion metals. The review contrasts theoretical consideration with recent experimental data collected on both heavy fermion metals (HF) and frustrated insulators. Such a method allows to understand experimental data. We also consider experimental data collected on quantum spin liquid in and quasi-one dimensional (1D) quantum spin liquid in both and with the aim to establish a sound theoretical explanation for the observed scaling laws, Landau Fermi liquid (LFL) and non-Fermi-liquid (NFL) behavior exhibited by these frustrated insulators. The recent experimental data on the heavy-fermion metal , with , and on its sister compounds and , carried out under the application of magnetic field as a control parameter are analyzed. We show that the thermodynamic and transport properties as well as the empirical scaling laws follow from the fermion condensation theory. We explain how both the similarity and the difference in the thermodynamic and transport properties of and in its sister compounds and emerge, as well as establish connection of these (HF) metals with insulators , and . We demonstrate that the universal LFL and NFL behavior emerge because the HF compounds and the frustrated insulators are located near the topological FCQPT or are driven by the application of magnetic fields. 相似文献
13.
Gustavo A. Lombardi Kamal Mydeen Roman Gumeniuk Andreas Leithe-Jasper Walter Schnelle Ricardo D. dos Reis Michael Nicklas 《Materials》2022,15(8)
We carried out electrical resistivity and X-ray diffraction (XRD) studies on the filled skutterudite superconductors LaPtGe and PrPtGe under hydrostatic pressure. The superconducting transition temperature is linearly suppressed upon increasing pressure, though the effect of pressure on is rather weak. From the analysis of the XRD data, we obtain bulk moduli of GPa and GPa for LaPtGe and PrPtGe, respectively. The knowledge of the bulk modulus allows us to compare the dependence of on the unit-cell volume from our pressure study directly with that found in the substitution series LaPrPtGe. We find that application of hydrostatic pressure can be characterized mainly as a volume effect in LaPtGe and PrPtGe, while substitution of Pr for La in LaPrPtGe yields features going beyond a simple picture. 相似文献
14.
We report on X-ray photoelectron spectroscopy and ab initio electronic structure investigations of the skutterudite-related RhSn superconductors, where R = Sc, Y, and Lu. These compounds crystallise with a tetragonal structure (space group I) and are characterised by a deficiency of R atoms in their formula unit (RhSn, ). Recently, we documented that the vacancies and atomic local defects (often induced by doping) are a reason for the enhancement in the superconducting transition temperature of these materials, as well as metallic () or semimetallic () behaviours in their normal state. Our band structure calculations show the pseudogap at a binding energy of −0.3 eV for the stoichiometric compounds, which can be easily moved towards the Fermi level by vacancies . As a result, dychotomic nature in electric transport of RhSn (metallic or semimetallic resistivity) depends on , which has not been interpreted before. We have shown that the densities of states are very similar for various RhSn compounds, and they practically do not depend on the metal R, while they are determined by the Rh d-and Sn s- and p-electron states. The band structure calculations for ScRhSn have not been reported yet. We also found that the electronic specific heat coefficients for the stoichiometric samples were always larger with respect to the of the respective samples with vacancies at the R sites, which correlates with the results of ab initio calculations. 相似文献
15.
Alluaudite-type materials are systematically attracting more attention as prospective cathode materials for sodium ion batteries. In this paper, we strove to optimize various synthesis parameters of three alluaudite compositions (NaFe(PO)—FFF, NaVFe(PO)—VFF, and NaVFeMn(PO)—VFM) to obtain nanostructured alluaudite-type glass-ceramics with high phase purity. We systematically investigated the role of the chemical reactions, temperature and time of melting, cooling rate, and reducing factors on the quality of the final products. A detailed synthesis protocol along with X-ray diffractometry, thermal analysis, scanning electron microscopy imaging, and electrical conductivity measurements (with impedance spectroscopy) are reported. As a result, a significant increase of the conductivity was observed in the nanomaterials. The highest value was reached for the VFF composition and was equal to S/cm at room temperature. 相似文献
16.
Biodegradable pure iron has gained significant interest as a biomedical material. For biodegradable implant applications, the biodegradation behavior of pure iron is important. In this work, the influence of ferrite grain size on the biodegradation rate for pure iron was studied by means of heat treatment that was annealed below the austenized temperature using as-forged pure iron. Grains were coarsened and a spectrum of ferrite grain sizes was gained by changing the annealed temperature. Biodegradation behavior was studied through weight loss tests, electrochemical measurements and microscopic analyses. Hardness (HV) and biodegradation rate (Pi or Pw) were linearly ferrite grain size-dependent: , and or . The mechanism by which the role of grain size on biodegradation rate was attributed to the ferrite grain boundary traits. 相似文献
17.
Nickelate films have recently attracted broad attention due to the observation of superconductivity in the infinite layer phase of NdSrNiO (obtained by reducing Sr doped NdNiO films) and their similarity to the cuprates high temperature superconductors. Here, we report on the observation of a new type of transport in oxygen poor NdSrNiO films. At high temperatures, variable range hopping is observed while at low temperatures a novel tunneling behavior is found where a Josephson-like tunneling junction characteristic with serial resistance is revealed. We attribute this phenomenon to coupling between superconductive (S) surfaces of the grains in our Oxygen poor films via the insulating (I) grain boundaries, which yields SIS junctions in series with the normal (N) resistance of the grains themselves. The similarity of the observed conductance spectra to the tunneling junction characteristic with Josephson-like current is striking, and seems to support the existence of superconductivity in our samples. 相似文献
18.
Yurii G. Selivanov Victor P. Martovitskii Mikhail I. Bannikov Aleksandr Y. Kuntsevich 《Materials》2021,14(24)
Search for doped superconducting topological insulators is of prime importance for new quantum technologies. We report on fabrication of Sr-doped BiTe single crystals. We found that Bridgman grown samples have p-type conductivity in the low 10 cm, high mobility of 4000 cmVs, crystal structure independent on nominal dopant content, and no signs of superconductivity. We also studied molecular beam epitaxy grown SrBiTe films on lattice matched (1 1 1) BaF polar surface. Contrary to the bulk crystals thin films have n-type conductivity. Carrier concentration, mobility and c-lattice constant demonstrate pronounced dependence on Sr concentration x. Variation of the parameters did not lead to superconductivity. We revealed, that transport and structural parameters are governed by Sr dopants incorporation in randomly inserted Bi bilayers into the parent matrix. Thus, our data shed light on the structural position of dopant in BiTe and should be helpful for further design of topological insulator-based superconductors. 相似文献
19.
Josip Jakovac Leonardo Marui Denise Andrade-Guevara Julio C. Chacn-Torres Vito Despoja 《Materials》2021,14(15)
A theoretical formulation of the electromagnetic response in graphene ribbons on dielectric substrate is derived in the framework of the ab initio method. The formulation is applied to calculate the electromagnetic energy absorption in an array of potassium-doped graphene nanoribbons (KC-NR) deposited on a dielectric AlO substrate. It is demonstrated that the replacement of the flat KC by an array of KC-NR transforms the Drude tail in the absorption spectra into a series of infrared-active Dirac plasmon resonances. It is also shown that the series of Dirac plasmon resonances, when unfolded across the extended Brillouin zones, resembles the Dirac plasmon. The Dirac plasmon resonances’ band structure, within the first Brillouin zone, is calculated. Finally, an excellent agreement between the theoretical absorption and recent experimental results for differential transmission through graphene on an SiO/Si surface is presented. The theoretically predicted micrometer graphene nanoribbons intercalation compound (GNRIC) in a stage-I-like KC is confirmed to be synthesized for Dirac plasmon resonances. 相似文献
20.
Artyom Plyushch Nerijus Ma
iulis Aliaksei Sokal Robertas Grigalaitis Jan Macutkevi
Alexander Kudlash Natalia Apanasevich Konstantin Lapko Algirdas Selskis Sergey A. Maksimenko Polina Kuzhir Juras Banys 《Materials》2021,14(17)
Composite materials with 83 wt.% of the 0.7Pb(MgNb)O-0.3PbTiO distributed in phosphate-bonded ceramics were prepared at three different pressures. A phosphate matrix comprises a mixture of an aluminum phosphate binder and melted periclase, MgO. All samples demonstrate a homogeneous distribution of the ferroelectric perovskite phase and are thermally stable up to 900 K. At higher temperatures, the pyrochlore cubic phase forms. It has been found that the density of the composites non-monotonously depends on the pressure. The dielectric permittivity and losses substantially increase with the density of the samples. The fabricated composites demonstrate diffused ferroelectric–paraelectric transition and prominent piezoelectric properties. 相似文献