Synthesis and Crystal Growth of Tetragonal β‐Fe<sub>1.00</sub>Se

Koz, Cevriye; Schmidt, Marcus; Borrmann, Horst; Burkhardt, Ulrich; Rößler, Sahana; Carrillo‐Cabrera, W.; Schnelle, Walter; Schwarz, Ulrich; Grin, Yuri

doi:10.1002/zaac.201300670

Cited by 40 publications

(71 citation statements)

References 37 publications

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“…Clearly, there is a minor superparamagnetic-like ferromagnetic impurity, as can be expected when using iron metal as starting material and relatively low reaction temperatures. To quantify the impurity, the magnetization curve was extrapolated to zero field, and the obtained magnetization could then be compared with the saturation moments of either Fe metal (2.2 μ B per Fe) as done by Koz et al [10] or Fe 3 O 4 (4 μ B per formula unit). The extrapolated value is approximately 0.0025 μ B , which corresponds to 0.1 % Fe or 0.06 % Fe 3 O 4 , which is below the detection limit of the other analysis techniques, thereby emphasizing the sensitivity of the squid magnetometer.…”

Section: Resultsmentioning

confidence: 99%

S = 2 Spin Ladders in the Sulfide Oxide BaFe₂S₂O

et al. 2014

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Section: Resultsmentioning

confidence: 99%

S = 2 Spin Ladders in the Sulfide Oxide BaFe₂S₂O

et al. 2014

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“…By extrapolating back from the higher to zero magnetic fields, it is possible to extract the extrinsic ferromagnetic moment, as demonstrated by Koz et al. for an iron impurity in FeSe 21. Here, cobalt metal was used in the synthesis and can, thus, occur in the end product.…”

Section: Resultsmentioning

confidence: 99%

Synthesis and Characterization of Ba[CoSO]: Magnetic Complexity in the Presence of Chalcogen Ordering

Valldor

Rößler

Prots

et al. 2015

Chemistry A European J

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Barium thio-oxocobaltate(II), Ba[CoS2/2 O2/2 ], was synthesized by the reaction of equimolar amounts of BaO, Co, and S in closed silica ampoules. The title compound (Cmcm, a=3.98808(3), b=12.75518(9), c=6.10697(4) Å) is isostructural to Ba[ZnSO]. The use of soft X-ray absorption spectroscopy confirmed that cobalt is in the oxidation state +2 and tetrahedrally coordinated. Its coordination consists of two sulfur and two oxygen atoms in an ordered fashion. High-temperature magnetic susceptibility data indicate strong low-dimensional spin-spin interactions, which are suggested to be closely related to the layer-type crystal structure and perhaps the ordered distribution of sulfur and oxygen. Antiferromagnetic ordering below TN =222 K is observed as an anomaly in the specific heat, coinciding with a significant lowering of the magnetic susceptibility. Density functional theory calculations within a generalized-gradient approximation (GGA)+U approach identify an antiferromagnetic ground state within the square-like two-dimensional layers of Co, and antiferromagnetic correlations for nearest and next nearest neighbors along bonds mediated by oxygen or sulfur. However, this magnetic state is subject to frustration by relatively strong interlayer couplings.

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“…The high temperature structure of FeSe belongs to the tetragonal P4/nmm space group with the corresponding lattice parameters a = 3.77Å and c = 5.52Å [50][51][52]. Note that here a is the distance between nearest neighbor selenium atoms lying in the same plane.…”

Section: Crystal Structure: Labeling In the Orthorhombic Phasementioning

confidence: 99%

Discovery of orbital-selective Cooper pairing in FeSe

Sprau

Kostin

Kreisel

et al. 2017

Science

371

494

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FeSe is the focus of intense research interest because of its unusual non-magnetic nematic state and because it forms the basis for achieving the highest critical temperatures of any iron-based superconductor. However, its Cooper pairing mechanism has not been determined because an accurate knowledge of the momentum-space structure of superconducting energy gaps ∆ i ( k) on the different electron-bands E i ( k) does not exist. Here we use Bogoliubov quasiparticle interference (BQPI) imaging to determine the coherent Fermi surface geometry of the α-and ε-bands surrounding the Γ = (0, 0) and X = (π/a Fe , 0) points of FeSe, and to measure their superconducting energy gaps ∆ α ( k) and ∆ ε ( k).We show directly that both gaps are extremely anisotropic but nodeless, and are aligned along orthogonal crystal axes. Moreover, by implementing a novel technique we demonstrate the sign change between ∆ α ( k) and ∆ ε ( k). This complex configuration of ∆ α ( k) and ∆ ε ( k), which was unanticipated within pairing theories for FeSe, reveals a unique form of superconductivity based on orbital selective Cooper pairing of electrons from the d yz orbitals of iron atoms. This new paradigm of orbital selectivity may be pivotal to understanding the microscopic interplay of quantum paramagnetism, nematicity and high temperature superconductivity. BIOGRAPHICAL SKETCHPeter Oliver Sprau was born on June 13th 1986 in the small town of Kirchheimbolanden, Germany, where he completed both his primary and secondary education. Long before he was a physicist, Peter was an active member of the track and field team in his school and a local club, even going on to compete in the dash and relay event on the state and federal youth level. Upon finishing school, he fulfilled his civic duty and carried out his alternative civilian service in the hospital in Kirchheimbolanden. While Peter's academic interests were diverse, including not just science but also Latin and history, his natural curiosity about the world finally urged him to pursue a higher education in physics. Mistakes. Make glorious, amazing mistakes. Make mistakes nobody's ever made before. Don't freeze, don't stop, don't worry that it isn't good enough, or it isn't perfect, whatever it is: art, or love, or work or family or life.Whatever it is you're scared of doing, Do it. Make your mistakes, next year and forever." I also want to acknowledge in no specific order the following people for useful discussions throughout my PhD:

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Synthesis and Crystal Growth of Tetragonal β‐Fe_1.00Se

Cited by 40 publications

References 37 publications

S = 2 Spin Ladders in the Sulfide Oxide BaFe₂S₂O

S = 2 Spin Ladders in the Sulfide Oxide BaFe₂S₂O

Synthesis and Characterization of Ba[CoSO]: Magnetic Complexity in the Presence of Chalcogen Ordering

Discovery of orbital-selective Cooper pairing in FeSe

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Synthesis and Crystal Growth of Tetragonal β‐Fe1.00Se

Cited by 40 publications

References 37 publications

S = 2 Spin Ladders in the Sulfide Oxide BaFe2S2O

S = 2 Spin Ladders in the Sulfide Oxide BaFe2S2O

Synthesis and Characterization of Ba[CoSO]: Magnetic Complexity in the Presence of Chalcogen Ordering

Discovery of orbital-selective Cooper pairing in FeSe

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Synthesis and Crystal Growth of Tetragonal β‐Fe_1.00Se

S = 2 Spin Ladders in the Sulfide Oxide BaFe₂S₂O

S = 2 Spin Ladders in the Sulfide Oxide BaFe₂S₂O