218 research outputs found
Coexistence of ferromagnetism and superconductivity in the hybrid ruthenate-cuprate compound RuSr_2GdCu_2O_8 studied by muon spin rotation (\mu SR) and DC-magnetization
We have investigated the magnetic and the superconducting properties of the
hybrid ruthenate-cuprate compound RuSr_{2}GdCu_{2}O_{8} by means of zero-field
muon spin rotation- (ZF-SR) and DC magnetization measurements. The
DC-magnetisation data establish that this material exhibits ferromagnetic order
of the Ru-moments () below T_{Curie} = 133 K and
becomes superconducting at a much lower temperature T_c = 16 K. The ZF-SR
experiments indicate that the ferromagnetic phase is homogeneous on a
microscopic scale and accounts for most of the sample volume. They also suggest
that the magnetic order is not significantly modified at the onset of
superconductivity.Comment: improved version submitted to Phys. Rev.
Two dimensionality in quasi one-dimensional cobalt oxides
By means of muon spin rotation and relaxation (SR) techniques, we have
investigated the magnetism of quasi one-dimensional (1D) cobalt oxides
CoO (=Ca, Sr and Ba, =1, 2, 3, 5 and
), in which the 1D CoO chain is surrounded by six equally spaced
chains forming a triangular lattice in the -plane, using polycrystalline
samples, from room temperature down to 1.8 K. For the compounds with =1 - 5,
transverse field SR experiments showed the existence of a magnetic
transition below 100 K. The onset temperature of the transition () was found to decrease with ; from 100 K for =1 to 60 K for
=5. A damped muon spin oscillation was observed only in the sample with
=1 (CaCoO), whereas only a fast relaxation obtained even at 1.8
K in the other three samples. In combination with the results of susceptibility
measurements, this indicates that a two-dimensional short-range
antiferromagnetic (AF) order appears below for all
compounds with =1 - 5; but quasi-static long-range AF order formed only in
CaCoO, below 25 K. For BaCoO (=), as decreased
from 300 K, 1D ferromagnetic (F) order appeared below 53 K, and a sharp 2D AF
transition occurred at 15 K.Comment: 12 pages, 14 figures, and 2 table
An H-TERT Mutated Skin Metastasis as First Occurrence in a Case of Follicular Thyroid Carcinoma
Differentiated thyroid cancer arising from thyroid follicular epithelial cells is the most frequent endocrine malignancy, and skin metastases are very rare. We describe a case of a 70-year-old women with a history of an indeterminate thyroid nodule on cytology. A painless, erythematous skin nodule of about 7 mm diameter was removed from the scalp and diagnosed as a metastasis from thyroid cancer. After total thyroidectomy, a histological diagnosis of follicular thyroid cancer was made. Two cycles of radioactive iodine were performed. Both the follicular thyroid carcinoma and the metastasis were investigated for the presence of BRAF/RAS and TERT promoter mutations. The results showed that the cutaneous metastasis was BRAF wild-type and TERT promoter-mutated (position g.1,295,228 C>T); in contrast, the primary thyroid lesion was negative for both molecular markers
Evidence for endohedral muonium in Kx C60 and consequences for electronic structure
Positive muons injected into solid C60, K4C60, and K6C60 form vacuumlike muonium (μ+e-) with a (6–12)% probability. Observation of coherent spin precession of muonium establishes that all three materials are nonmagnetic and nonconducting at low temperatures. From the temperature dependence of the signals we estimate the electronic band gaps in K4C60 and K6C60 to be considerably smaller than in C60. The similarity of the muonium centers supports a model in which a muonium atom is caged inside the C60 molecule in pure C60 or the C60x molecular ion in KxC60
Freezing of spin and charge in La_(2-x)Sr_xCuO_4
Zero- and longitudinal-field muon-spin relaxation μ+SR measurements have been performed on La_(2-x)Sr_xCuO_4 alloys in both single-crystal and sintered powder forms above and below their magnetic transition temperatures, T_f. The μ+ precession frequency v depends only weakly on x and T_f, an observation which together with resistivity data implies classical freezing of magnetic moments in the regime where the carriers are localized. For x=0.05, critical dynamics are observed near T_f. The μ^+SR technique is shown to be very sensitive to ferromagnetically aligned pairs of Cu^(2+) moments; the population of such pairs increases greatly with x
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Mechanisms of change in the evolution of jargon aphasia
Background: The evolution of jargon aphasia may reflect recovery in the speech production processes. Alternatively or additionally there may be improved self-monitoring, enabling the person to suppress jargon errors. Previous case reports offer evidence for both mechanisms of change, and suggest that they can co-occur.
Aims: This longitudinal study aimed to uncover mechanisms of change in an individual with jargon aphasia. Four predictions of production processing recovery were examined against test data. The study also looked for evidence of improved error awareness, in both test and connected speech data, and explored the relationship between this improvement and the production gains.
Methods & Procedures: The participant (TK) undertook tests of single word naming, reading and repetition eight times over a 21-month period, with matched sets of nouns and verbs. Analyses of correct responses and errors were conducted, in order to test predictions of processing recovery. Changes in self-monitoring behaviours were also investigated, to uncover evidence of increased error awareness. Finally, longitudinal changes in samples of connected speech were explored.
Outcomes & Results: Two predictions of production processing recovery were upheld: there was a significant increase in the number of correct responses over time, and a significant decrease in the proportion of nonword errors. The error analysis also revealed a trend towards increased target-relatedness and decreased perseveration, but neither was significant. There was an increase in self-monitoring behaviours during testing, in that there were more null responses and attempted self-corrections. This increase correlated very strongly with the production gains. Connected speech showed little evidence of improved production, since the range of vocabulary employed by TK reduced as time progressed. However, self-monitoring behaviours were increasingly evident in this context.
Conclusions: The origin of the production and monitoring gains experienced by TK are discussed. Implications are drawn out for further research
A common behavior of thermoelectric layered cobaltites: incommensurate spin density wave states in [CaCoCuO][CoO] and [CaCoO][CoO]
Magnetism of a misfit layered cobaltite
[CaCoCuO][CoO] ( 0.62, RS
denotes a rocksalt-type block) was investigated by a positive muon spin
rotation and relaxation (SR) experiment. A transition to an
incommensurate ({\sf IC}) spin density wave ({\sf SDW}) state was found below
180 K (= ); and a clear oscillation due to a static
internal magnetic field was observed below 140 K (= ). Furthermore,
an anisotropic behavior of the zero-field SR experiment indicated that
the {\sf IC-SDW} propagates in the - plane, with oscillating moments
directed along the c axis. These results were quite similar to those for the
related compound [CaCoO][CoO], {\sl i.e.},
CaCoO. Since the {\sf IC-SDW} field in
[CaCoCuO][CoO] was approximately
same to those in pure and doped [CaCoO][CoO], it
was concluded that the {\sf IC-SDW} exist in the [CoO] planes.Comment: 15 pages, 6 figures. accepted for publication in J. Phys.: Condens.
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