Fermi Surface of Cr1−x_{1-x}Vx_x across the Quantum Critical Point

We have measured de Haas-van Alphen oscillations of Cr$_{1-x}$V$_x$, $0 \le x \le 0.05$, at high fields for samples on both sides of the quantum critical point at $x_c=0.035$. For all samples we observe only those oscillations associated with a single small hole band with magnetic breakdown orbits of the reconstructed Fermi surface evident for $x<x_c$. The absence of oscillations from Fermi surface sheets most responsible for the spin density wave (SDW) in Cr for $x>x_c$ is further evidence for strong fluctuation scattering of these charge carriers well into the paramagnetic regime. We find no significant mass enhancement of the carriers in the single observed band at any $x$. An anomalous field dependence of the dHvA signal for our $x=0.035$ crystal at particular orientations of the magnetic field is identified as due to magnetic breakdown that we speculate results from a field induced SDW transition at high fields.Comment: 8 pages with 7 figure

High Resolution Study of Magnetic Ordering at Absolute Zero

High fidelity pressure measurements in the zero temperature limit provide a unique opportunity to study the behavior of strongly interacting, itinerant electrons with coupled spin and charge degrees of freedom. Approaching the exactitude that has become the hallmark of experiments on classical critical phenomena, we characterize the quantum critical behavior of the model, elemental antiferromagnet chromium, lightly doped with vanadium. We resolve the sharp doubling of the Hall coefficient at the quantum critical point and trace the dominating effects of quantum fluctuations up to surprisingly high temperatures.Comment: 5 pages, 4 figure

First-Principles Dynamical Coherent-Potential Approximation Approach to the Ferromagnetism of Fe, Co, and Ni

Magnetic properties of Fe, Co, and Ni at finite temperatures have been investigated on the basis of the first-principles dynamical CPA (Coherent Potential Approximation) combined with the LDA (Local Density Approximation) + $U$ Hamiltonian in the Tight-Binding Linear Muffintin Orbital (TB-LMTO) representation. The Hamiltonian includes the transverse spin fluctuation terms. Numerical calculations have been performed within the harmonic approximation with 4th-order dynamical corrections. Calculated single-particle densities of states in the ferromagnetic state indicate that the dynamical effects reduce the exchange splitting, suppress the band width of the quasi-particle state, and causes incoherent excitations corresponding the 6 eV satellites. Results of the magnetization vs temperature curves, paramagnetic spin susceptibilities, and the amplitudes of local moments are presented. Calculated Curie temperatures ($T_{\rm C}$) are reported to be 1930K for Fe, 2550K for Co, and 620K for Ni; $T_{\rm C}$ for Fe and Co are overestimated by a factor of 1.8, while $T_{\rm C}$ in Ni agrees with the experimental result. Effective Bohr magneton numbers calculated from the inverse susceptibilities are 3.0 $\mu_{\rm B}$ (Fe), 3.0 $\mu_{\rm B}$ (Co), and 1.6 $\mu_{\rm B}$ (Ni), being in agreement with the experimental ones. Overestimate of $T_{\rm C}$ in Fe and Co is attributed to the neglects of the higher-order dynamical effects as well as the magnetic short range order.Comment: 10 pages, 13 figure

TUMOUR NECROSIS FACTOR alpha IN RHEUMATOID ARTHRITIS AND OSTEOARTHRITIS PATIENTS IN BLOOD SERUM AND SYNOVIAL FLUID

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Outpatient Care Aspects of Rheumatic Patients in Latvia : Real Life Data in the Context of the First Month of the COVID-19 Pandemic

Publisher Copyright: © 2023 Julija Zepa et al., published by Sciendo.The aim of this study was to analyse the rheumatic disease profile and treatment aspects of the patients consulted in the outpatient department of Pauls Stradiņš Clinical University Hospital during the first month of the COVID-19 pandemic from 2020 March 13 till April 14. A total of 457 (76.04%) remote and 144 (23.96%) face-to-face consultations were analysed, totalling 601 patients: 434 (72.21%) females and 167 (27.79%) males with mean age 51.40 ± 14.73 years. Rheumatoid arthritis (223 (37.10%)), psoriatic arthritis (93 (15.47%)) and ankylosing spondylitis (80 (13.31%)) were the most frequently consulted conditions. Disease modifying antirheumatic drugs (DMARDs) or immunosuppressants (IS) were taken by 515 (85.69%) patients. These included synthetic DMARD (242 (46.99%)), mainly methotrexate; and biologic DMARD (156 (30.29%)), mainly tumour necrosis factor inhibitor. More than one-half of the cohort (427 (71.05%)) was not taking a glucocorticoid (GC). NSAIDs were used in 391 (65.08%) patients, mainly on demand (354 (90.54%)). Most patients (401 (66.72%)) had no comorbidities (hypertension, diabetes, malignancy and/or chronic respiratory disease). The profile of patients consulted in the outpatient department consisted mainly of middle-age females with autoimmune inflammatory arthritis treated by DMARD. Most of the patients did not use GCs, they did not regularly use NSAIDs and did not have comorbidities. Telemedicine is an acceptable way of care delivery for chronic rheumatic patients with previously known disease and treatment, especially during a pandemic.publishersversionPeer reviewe

Structure and magnetic properties of sputtered thin films of Fe 0.79

The full text of this article is not available on SOAR. WSU users can access the article via IEEE Xplore database licensed by University Libraries: http://libcat.wichita.edu/vwebv/holdingsInfo?bibId=1045954Films of Fe0.79Ge0.21 with thicknesses of 300 nm were synthesized by ion beam sputtering, and were annealed at temperatures from 200 to 550°C. The materials were characterized by x-ray diffractometry, Mössbauer spectrometry, vibrating sample magnetometry, ferromagnetic resonance spectrometry, and electrical resistivity measurements. The as-prepared materials comprised chemically disordered bcc crystallites of sizes less than 20 nm, and were found to have a distribution of internal strains. Upon annealing at temperatures of 250°C and below, there occurred strain relaxation, some evolution of short range chemical order, and an improvement in soft magnetic properties. The coercive field was a minimum for the sample annealed at 250°C. Crystallite growth occurred at higher annealing temperatures, accompanied by a transition in several measured parameters from those of ultrafine grained materials to those typical of polycrystalline materials. This trend can be explained with the random anisotropy model. Mössbauer and magnetization measurements indicated that the Ge atoms behave as magnetic holes. The 57Fe hyperfine magnetic field distribution, and its change during chemical ordering, can be calculated approximately with a model of magnetic response. The large local isomer shifts at 57Fe atoms near Ge atoms suggest that a local depletion of 4s conduction electron density should be incorporated into the model.Peer reviewed articl