13 research outputs found
Spin fluctuations in iron pnictides and chalcogenides: From antiferromagnetism to superconductivity
The present article reviews recent experimental investigations of spin
dynamics in iron-based superconductors and their parent compounds by means of
inelastic neutron scattering. It mainly focuses on the most contemporary
developments in this field, pertaining to the observations of magnetic resonant
modes in new superconductors, spin anisotropy of low-energy magnetic
fluctuations that has now been observed in a wide range of chemical
compositions and doping levels, as well as their momentum-space anisotropy
incurred by the spin-nematic order. The implications of these new findings for
our understanding of the superconducting state, along with the remaining
unsettled challenges for neutron spectroscopy, are discussed.Comment: Invited review article for a focus issue of Comptes Rendus Physique:
40 pages, 22 figures, 389 reference
Editorial on Research Topic: High-Tc Superconductivity in Electron-Doped Iron Selenide and Related Compounds
In this editorial, we first give a brief survey of the field of iron-selenide
superconductivity, both in the case of bulk FeSe characterized by the
co-existence of superconductivity and nematic order, and in the case of
electron-doped FeSe characterized by high-temperature superconductivity. We
next review the 8 contributions to the Frontiers in Physics research topic
"High-Tc Superconductivity in Electron-Doped Iron Selenide and Related
Compounds".Comment: 3 page
Adherence of the rotating vortex lattice in the noncentrosymmetric superconductor Ru7B3 to the London model
The noncentrosymmetric superconductor Ru7B3 has in previous studies demonstrated remarkably unusual behaviour in its vortex lattice, where the nearest neighbour directions of the vortices dissociate from the crystal lattice and instead show a complex field-history dependence, and the vortex lattice rotates as the field is changed. In this study, we look at the vortex lattice form factor of Ru7B3 during this field-history dependence, to check for deviations from established models, such as the London model. We find that the data is well described by the anisotropic London model, which is in accordance with theoretical predictions that the alterations to the structure of the vortices due to broken inversion symmetry should be small. From this, we also extract values for the penetration depth and coherence length. [Abstract copyright: Creative Commons Attribution license.
Rich Magnetic Phase Diagram of Putative Helimagnet SrFeO
The cubic perovskite SrFeO was recently reported to host hedgehog- and
skyrmion-lattice phases in a highly symmetric crystal structure which does not
support the Dzyaloshinskii-Moriya interactions commonly invoked to explain such
magnetic order. Hints of a complex magnetic phase diagram have also recently
been found in powder samples of the single-layer Ruddlesden-Popper analog
SrFeO, so a reinvestigation of the bilayer material SrFeO,
believed to be a simple helimagnet, is called for. Our magnetization and
dilatometry studies reveal a rich magnetic phase diagram with at least 6
distinct magnetically ordered phases and strong similarities to that of
SrFeO. In particular, at least one phase is apparently
multiple-, and the s are not observed to vary among the
phases. Since SrFeO has only two possible orientations for its
propagation vector, some of the phases are likely exotic multiple-
order, and it is possible to fully detwin all phases and more readily access
their exotic physics.Comment: 14 pages, 13 figure
Incommensurate and multiple- magnetic misfit order in the frustrated quantum spin ladder material antlerite, CuSO(OH)
In frustrated magnetic systems, the competition amongst interactions can
introduce extremely high degeneracy and prevent the system from readily
selecting a unique ground state. In such cases, the magnetic order is often
exquisitely sensitive to the balance among the interactions, allowing tuning
among novel magnetically ordered phases. In antlerite, CuSO(OH),
Cu () quantum spins populate three-leg zigzag ladders in a highly
frustrated quasi-one-dimensional structural motif. We demonstrate that at zero
applied field, in addition to its recently reported low-temperature phase of
coupled ferromagnetic and antiferromagnetic spin chains, this mineral hosts an
incommensurate helical+cycloidal state, an idle-spin state, and a multiple-
phase which is the magnetic analog of misfit crystal structures. The
antiferromagnetic order on the central leg is reentrant. The high tunability of
the magnetism in antlerite makes it a particularly promising platform for
pursuing exotic magnetic order.Comment: 18.3 pages, 16 Figures, follow-up paper to arXiv:2203.1534
Coupled frustrated ferromagnetic and antiferromagnetic quantum spin chains in the quasi-one-dimensional mineral antlerite Cu3 SO4 (OH) 4
Magnetic frustration, the competition among exchange interactions, often leads to novel magnetic ground states with unique physical properties which can hinge on details of interactions that are otherwise difficult to observe. Such states are particularly interesting when it is possible to tune the balance among the interactions to access multiple types of magnetic order. We present antlerite Cu3SO4(OH)4 as a potential platform for tuning frustration. Contrary to previous reports, the low-temperature magnetic state of its three-leg zigzag ladders is a quasi-one-dimensional analog of the magnetic state recently proposed to exhibit spinon-magnon mixing in botallackite. Density functional theory calculations indicate that antlerite's magnetic ground state is exquisitely sensitive to fine details of the atomic positions, with each chain independently on the cusp of a phase transition, indicating an excellent potential for tunability.This project was funded by the German Research Foundation (DFG) via the projects A05, C01, C03, and C06 of the Collaborative Research Center SFB 1143 (project-id 247310070); GRK 1621 (project-id 129760637); the Würzburg-Dresden Cluster of Excellence on Complexity and Topology in Quantum Matter—ct.qmat (EXC 2147, project-id 390858490); through individual research grants, Grants No. IN 209/9-1 and No. PE 3318/2-1; and through project-id 422219907. D.K. and O.J. were supported by the Leibniz Association through the Leibniz Competition.Peer reviewe
Stripe-yz magnetic order in the triangular-lattice antiferromagnet KCeS2
Yb- and Ce-based delafossites were recently identified as effective spin-1/2 antiferromagnets on the triangular lattice. Several Yb-based systems, such as NaYbO2, NaYbS2, and NaYbSe2, exhibit no long-range order down to the lowest measured temperatures and therefore serve as putative candidates for the realization of a quantum spin liquid. However, their isostructural Ce-based counterpart KCeS2 exhibits magnetic order below TN = 400 mK, which was so far identified only in thermodynamic measurements. Here we reveal the magnetic structure of this long-range ordered phase using magnetic neutron diffraction. We show that it represents the so-called 'stripe-yz' type of antiferromagnetic order with spins lying approximately in the triangular-lattice planes orthogonal to the nearest-neighbor Ce–Ce bonds. No structural lattice distortions are revealed below TN, indicating that the triangular lattice of Ce3+ ions remains geometrically perfect down to the lowest temperatures. We propose an effective Hamiltonian for KCeS2, based on a fit to the results of ab initio calculations, and demonstrate that its magnetic ground state matches the experimental spin structure.This project was funded in part by the German Research Foundation (DFG) under the individual research Grant IN 209/9-1, via the project C03 of the Collaborative Research Center SFB 1143 (project-id 247310070) at the TU Dresden, and the Würzburg-Dresden Cluster of Excellence on Complexity and Topology in Quantum Matter—ct.qmat (EXC 2147, project-id 390858490). SA thanks A Popov (IFW, Dresden) and M Vojta (TU Dresden) for fruitful discussions and acknowledges financial support from the German Research Foundation (DFG) under Grant No. AV 169/3-1. We also acknowledge V Joyet and S Djellit for technical assistance and Institut Laue-Langevin, Grenoble (France) for providing neutron beam time.Peer reviewe
Adherence of the rotating vortex lattice in the noncentrosymmetric superconductor Ru7B3 to the London model
The noncentrosymmetric superconductor Ru7B3has in previous studies demonstrated remarkably unusual behaviour in its vortex lattice (VL), where the nearest neighbour directions of the vortices dissociate from the crystal lattice and instead show a complex field-history dependence, and the VL rotates as the field is changed. In this study, we look at the VL form factor of Ru7B3during this field-history dependence, to check for deviations from established models, such as the London model. We find that the data is well described by the anisotropic London model, which is in accordance with theoretical predictions that the alterations to the structure of the vortices due to broken inversion symmetry should be small. From this, we also extract values for the penetration depth and coherence length.ISSN:0953-8984ISSN:1361-648
Stripe-yzmagnetic order in the triangular-lattice antiferromagnet KCeS2
Yb- and Ce-based delafossites were recently identified as effective spin-1/2 antiferromagnets on the triangular lattice. Several Yb-based systems, such as NaYbO2, NaYbS2, and NaYbSe2, exhibit no long-range order down to the lowest measured temperatures and therefore serve as putative candidates for the realization of a quantum spin liquid. However, their isostructural Ce-based counterpart KCeS2 exhibits magnetic order below TN = 400 mK, which was so far identified only in thermodynamic measurements. Here we reveal the magnetic structure of this long-range ordered phase using magnetic neutron diffraction. We show that it represents the so-called 'stripe-yz' type of antiferromagnetic order with spins lying approximately in the triangular-lattice planes orthogonal to the nearest-neighbor Ce–Ce bonds. No structural lattice distortions are revealed below TN, indicating that the triangular lattice of Ce3+ ions remains geometrically perfect down to the lowest temperatures. We propose an effective Hamiltonian for KCeS2, based on a fit to the results of ab initio calculations, and demonstrate that its magnetic ground state matches the experimental spin structure
Extreme Biomimetics: Designing of the First Nanostructured 3D Spongin–Atacamite Composite and its Application
The design of new composite materials using extreme biomimetics is of crucial importance for bioinspired materials science. Further progress in research and application of these new materials is impossible without understanding the mechanisms of formation, as well as structural features at the molecular and nano-level. It presents a challenge to obtain a holistic understanding of the mechanisms underlying the interaction of organic and inorganic phases under conditions of harsh chemical reactions for biopolymers. Yet, an understanding of these mechanisms can lead to the development of unusual—but functional—hybrid materials. In this work, a key way of designing centimeter-scale macroporous 3D composites, using renewable marine biopolymer spongin and a model industrial solution that simulates the highly toxic copper-containing waste generated in the production of printed circuit boards worldwide, is proposed. A new spongin–atacamite composite material is developed and its structure is confirmed using neutron diffraction, X-ray diffraction, high-resolution transmission electron microscopy/selected-area electron diffraction, X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure spectroscopy, and electron paramagnetic resonance spectroscopy. The formation mechanism for this material is also proposed. This study provides experimental evidence suggesting multifunctional applicability of the designed composite in the development of 3D constructed sensors, catalysts, and antibacterial filter systems