205 research outputs found
Half-Metallic Ferromagnetism in the Heusler Compound CoFeSi revealed by Resistivity, Magnetoresistance, and Anomalous Hall Effect measurements
We present electrical transport data for single-crystalline CoFeSi which
provide clear-cut evidence that this Heusler compound is truly a half-metallic
ferromagnet, i.e. it possesses perfect spin-polarization. More specifically,
the temperature dependence of is governed by electron scattering off
magnons which are thermally excited over a sizeable gap
() separating the electronic majority states at the Fermi level
from the unoccupied minority states. As a consequence, electron-magnon
scattering is only relevant at but freezes out at lower
temperatures, i.e., the spin-polarization of the electrons at the Fermi level
remains practically perfect for . The gapped magnon population
has a decisive influence on the magnetoresistance and the anomalous Hall effect
(AHE): i) The magnetoresistance changes its sign at , ii) the
anomalous Hall coefficient is strongly temperature dependent at and compatible with Berry phase related and/or side-jump electronic
deflection, whereas it is practically temperature-independent at lower
temperatures
Low-temperature properties of single-crystal CrB
We report the low-temperature properties of B-enriched single-crystal
CrB as prepared from high-purity Cr and B powder by a solid-state
reaction and optical float zoning. The electrical resistivity, ,
Hall effect, , and specific heat, , are characteristic of an
exchange-enhanced Fermi liquid ground state, which develops a slightly
anisotropic spin gap below . This observation is corroborated by the absence of a Curie dependence in
the magnetization for reported in the literature. Comparison of
with , where we infer lattice contributions from
measurements of VB, reveals strong antiferromagnetic spin fluctuations with
a characteristic spin fluctuation temperature
in the paramagnetic state, followed by a pronounced second-order mean-field
transition at , and unusual excitations around . The pronounced anisotropy of above is
characteristic of an easy-plane anisotropy of the spin fluctuations consistent
with the magnetization. The ratio of the Curie-Weiss to the Nel
temperatures, , inferred from the
magnetization, implies strong geometric frustration. All physical properties
are remarkably invariant under applied magnetic fields up to ,
the highest field studied. In contrast to earlier suggestions of local-moment
magnetism our study identifies CrB as a weak itinerant antiferromagnet
par excellence with strong geometric frustration.Comment: 15 pages, 9 figure
Seebeck coefficients of half-metallic ferromagnets
In this report the Co2 based Heusler compounds are discussed as potential
materials for spin voltage generation. The compounds were synthesized by
arcmelting and consequent annealing. Band structure calculations were performed
and revealed the compounds to be half-metallic ferromagnets. Magnetometry was
performed on the samples and the Curie temperatures and the magnetic moments
were determined. The Seebeck coefficients were measured from low to ambient
temperatures for all compounds. For selected compounds high temperature
measurements up to 900 K were performed.Comment: accepted contribution o the Special Issue "Spin Caloritronics" of
Solid State Communication
Brolucizumab in Neovascular Age-Related Macular Degeneration and Diabetic Macular Edema: Ophthalmology and Diabetology Treatment Aspects.
Anti-vascular endothelial growth factor (anti-VEGF) therapies have become the standard of care in the treatment of neovascular age-related macular degeneration (nAMD) and diabetic macular edema (DME), resulting in a remarkable decrease in disease-related vision loss. However, the need for regular injections places a significant burden on patients, caregivers, and the healthcare system and improvements in vision may not be maintained long term. As a result of its drying potency and duration of action, brolucizumab, an intravitreal anti-VEGF therapy approved for the treatment of nAMD and DME, could decrease injection frequency for patients and provide an efficacious treatment; however, balancing its benefits and risks can be challenging. There have been reports of intraocular inflammation (IOI) in patients treated with brolucizumab, which, if left untreated, may result in severe vision loss. Recent evidence, however, indicates that early recognition of IOI and prompt and aggressive systemic corticosteroid treatment in response to posterior segment involvement can lead to favorable outcomes in these relatively rare but severe cases. A series of consensus meetings were conducted in 2022 between Swiss medical retina experts and diabetologists, discussing the current data for brolucizumab and exploring various challenges to its use, including the associated risk of IOI. The outcome is a collation of practical insights and guidance for ophthalmologists on the use of brolucizumab in patients with nAMD and DME, including patient selection and assessment, treatment regimen and monitoring, and the recognition and management of adverse events
Crystal Growth and Electronic Phase Diagram of 4\u3cem\u3ed\u3c/em\u3e-doped Na\u3csub\u3e1-\u3cem\u3eδ\u3c/em\u3e\u3c/sub\u3eFe\u3csub\u3e1-\u3cem\u3ex\u3c/em\u3e\u3c/sub\u3eRh\u3csub\u3e\u3cem\u3ex\u3c/em\u3e\u3c/sub\u3eAs in Comparison to 3\u3cem\u3ed\u3c/em\u3e-doped Na\u3csub\u3e1-\u3cem\u3eδ\u3c/em\u3e\u3c/sub\u3eFe\u3csub\u3e1-\u3cem\u3ex\u3c/em\u3e\u3c/sub\u3eCo\u3csub\u3e\u3cem\u3ex\u3c/em\u3e\u3c/sub\u3eAs
Single crystals of Na1−δFe1−xTxAs with T = Co, Rh have been grown using a self-flux technique. The crystals were thoroughly characterized by powder x-ray diffraction, magnetic susceptibility, and electronic transport with particular focus on the Rh-doped samples. Measurements of the specific heat and ARPES were conducted exemplarily for the optimally doped compositions. The spin-density wave transition (SDW) observed for samples with low Rh concentration (0≤x≤0.013) is fully suppressed in the optimally doped sample. The superconducting transition temperature (Tc) is enhanced from 10 K in Na1−δFeAs to 21 K in the optimally doped sample (x=0.019) of the Na1−δFe1−xRhxAs series and decreases for the overdoped compounds, revealing a typical shape for the superconducting part of the electronic phase diagram. Remarkably, the phase diagram is almost identical to that of Co-doped Na1−δFeAs, suggesting a generic phase diagram for both dopants
Going chiral: overlap versus twisted mass fermions
We compare the behavior of overlap fermions, which are chirally invariant,
and of Wilson twisted mass fermions at full twist in the approach to the chiral
limit. Our quenched simulations reveal that with both formulations of lattice
fermions pion masses of O(250 MeV) can be reached in practical applications.
Our comparison is done at a fixed value of the lattice spacing a=0.123 fm. A
number of quantities are measured such as hadron masses, pseudoscalar decay
constants and quark masses obtained from Ward identities. We also determine the
axial vector renormalization constants in the case of overlap fermions.Comment: 22 pages, 10 figure
Weak localization of light by cold atoms: the impact of quantum internal structure
Since the work of Anderson on localization, interference effects for the
propagation of a wave in the presence of disorder have been extensively
studied, as exemplified in coherent backscattering (CBS) of light. In the
multiple scattering of light by a disordered sample of thermal atoms,
interference effects are usually washed out by the fast atomic motion. This is
no longer true for cold atoms where CBS has recently been observed. However,
the internal structure of the atoms strongly influences the interference
properties. In this paper, we consider light scattering by an atomic dipole
transition with arbitrary degeneracy and study its impact on coherent
backscattering. We show that the interference contrast is strongly reduced.
Assuming a uniform statistical distribution over internal degrees of freedom,
we compute analytically the single and double scattering contributions to the
intensity in the weak localization regime. The so-called ladder and crossed
diagrams are generalized to the case of atoms and permit to calculate
enhancement factors and backscattering intensity profiles for polarized light
and any closed atomic dipole transition.Comment: 22 pages Revtex, 9 figures, to appear in PR
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