566 research outputs found
Macroscopic phase segregation in superconducting K0.73Fe1.67Se2 as seen by muon spin rotation and infrared spectroscopy
Using muon spin rotation (\muSR) and infrared spectroscopy we investigated
the recently discovered superconductor K0.73Fe1.67Se2 with Tc = 32 K. We show
that the combined data can be consistently described in terms of a
macroscopically phase segregated state with a matrix of ~88% volume fraction
that is insulating and strongly magnetic and inclusions with a ~12% volume
fraction which are metallic, superconducting and non-magnetic. The electronic
properties of the latter, in terms of the normal state plasma frequency and the
superconducting condensate density, appear to be similar as in other iron
selenide or arsenide superconductors.Comment: 22 pages, 8 figures. (citation list correction.
Magnetic Phase Diagram of the Hole-doped CaNaCuOCl Cuprate Superconductor
We report on the magnetic phase diagram of a hole-doped cuprate
CaNaCuOCl, which is free from buckling of CuO
planes, determined by muon spin rotation and relaxation. It is characterized by
a quasi-static spin glass-like phase over a range of sodium concentration
(), which is held between long range antiferromagnetic
(AF) phase () and superconducting phase where the system is
non-magnetic for . The obtained phase diagram qualitatively agrees
well with that commonly found for hole-doped high-\tc cuprates, strongly
suggesting that the incomplete suppression of the AF order for is an
essential feature of the hole-doped cuprates.Comment: 5 pages, submitted to Phys. Rev. Let
Muon spin rotation study of magnetism and superconductivity in BaFe2-xCoxAs2 and Pr1-xSrxFeAsO
We present a muon spin rotation (\muSR) study of the magnetic and
superconducting properties of single crystals of electron-doped BaFe2-xCoxAs2
with x=0.08, 0.20, and 0.25 (Tc=9, 25 and 20K) and of polycrystalline
hole-doped Pr1-xSrxFeAsO with x=0 and 0.2 (Tc=15 K). In the former series we
observe some interesting parallels with the electron doped SmFeAsO1-xFx
1111-type system [A.J. Drew et al., to appear in Nature Materials 2009 and
arXiv:0807.4876]. In particular, we obtain evidence that strongly disordered
static magnetism coexists with superconductivity on a microscopic scale in
underdoped samples and even at optimum doping there is a slowing down (or
enhancement) of dynamic magnetic correlations below Tc\approx25K. To the
contrary, for the hole-doped Pr1-xSrxFeAsO samples we obtain evidence for a
mesoscopic phase segregation into regions with nearly unperturbed AF order and
others that are non magnetic and most likely superconducting. The observed
trend resembles the one that was previously reported for hole-doped
Ba1-xKxFe2As2 [A.A. Aczel et al., Phys. Rev. B 78, 214503 (2008); J.T. Park et
al., arXiv:0811.2224] and thus seems to be fairly common in these hole doped
systems.Comment: 17 pages, 6 figure
Coexistence of static magnetism and superconductivity in SmFeAsO1-xFx as revealed by muon spin rotation
The recent observation of superconductivity with critical temperatures up to
55 K in the FeAs based pnictide compounds marks the first discovery of a non
copper-oxide based layered high-Tc superconductor (HTSC) [1-3]. It has raised
the suspicion that these new materials share a similar pairing mechanism to the
cuprates, since both exhibit superconductivity following charge doping of a
magnetic parent material. Here we present a muon spin rotation study on
SmFeAsO1-xFx (x=0-0.30), which shows that static magnetism persists well into
the superconducting regime. The analogy with the cuprates is quite surprising
since the parent compounds appear to have different magnetic ground states:
itinerant spin density wave for the pnictides contrasted with the Mott-Hubbard
insulator in the cuprates. Our findings suggest that proximity to magnetic
order and associated soft magnetic fluctuations, rather than the strong
electronic correlations in the vicinity of a Mott-Hubbard-metal-to-insulator
transition, may be the key ingredients of HTSC.Comment: Accepted in Nature Material
Outcomes of Operatively Treated Acute Knee Dislocations
Knee dislocation is a complex and rare injury often presenting in the context of high velocity trauma. The aim of this study is to establish the subjective outcomes of surgically treated knee dislocations. A total of 20 knees dislocations treated by open repair were reviewed. Their progress and outcomes were assessed by using a modified Lysholm score questionnaire. Data was obtained on patient demographics, details of injury, investigation, treatment, rehabilitation, 24 months objective outcome and subjective outcomes. Six patients had a vascular deficit and six had neurological deficits. The median range of motion was 0°-100°. Patients with an initially lower pre-injury level of function were able to return an activity level comparable to their pre-injury status. 22% of competitive athletes retuned to competitive sports. 38% of patients undertaking heavy activity returned to comparable pre-injury level of activity and 67% of patients undertaking moderate level of activity before injury returned to a comparable level after repair. 68% regularly had problems running, 70% problem squatting, 40% swelling and 42% problem with stairs. Most patients however did not have locking of the knee or problems with knees giving way. Patients pain scores decreased over time to an acceptable level. Despite the severity of the injury, majority of patients achieved a satisfactory outcome, although none of the patients reached the same level of function as before the injury. 80% of the patients were satisfied with their outcome. All dissatisfied patients suffered postoperative complications
Evidence for the Re-Enactment of a Recently Learned Behavior during Sleepwalking
Animal studies have shown that sequenced patterns of neuronal activity may be replayed during sleep. However, the existence of such replay in humans has not yet been directly demonstrated. Here we studied patients who exhibit overt behaviors during sleep to test whether sequences of movements trained during the day may be spontaneously reenacted by the patients during sleep
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