162 research outputs found
Proximity effect of vanadium on spin-density-wave magnetism in Cr films
The spin-density wave (SDW) state in thin chromium films is well known to be
strongly affected by proximity effects from neighboring layers. To date the
main attention has been given to effects arising from exchange interactions at
interfaces. In the present work we report on combined neutron and synchrotron
scattering studies of proximity effects in Cr/V films where the boundary
condition is due to the hybridization of Cr with paramagnetic V at the
interface. We find that the V/Cr interface has a strong and long-range effect
on the polarization, period, and the N\'{e}el temperature of the SDW in rather
thick Cr films. This unusually strong effect is unexpected and not predicted by
theory.Comment: 7 figure
Strong coupling between magnetic and structural order parameters in SrFe2As2
X-ray and Neutron diffraction as well as muon spin relaxation and M\"ossbauer
experiments performed on SrFeAs polycrystalls confirm a sharp first
order transition at ,K corresponding to an orthorhombic phase
distortion and to a columnar antiferromagnetic Fe ordering with a propagation
vector (1,0,1), and a larger distortion and larger size of the ordered moment
than reported for BaFeAs. The structural and the magnetic order
parameters present an remarkable similarity in their temperature dependence
from down to low temperatures, showing that both phenomena are intimately
connected. Accordingly, the size of the ordered Fe moments scale with the
lattice distortion when going from SrFeAs to BaFeAs.
Full-potential band structure calculations confirm that the columnar magnetic
order and the orthorhombic lattice distortion are intrinsically tied to each
other.Comment: 10 pages, 4 figure
High Magnetic Field Behaviour of the Triangular Lattice Antiferromagnet, CuFeO_2
The high magnetic field behaviour of the triangular lattice antiferromagnet
CuFeO_2 is studied using single crystal neutron diffraction measurements in a
field of up to 14.5 T and also by magnetisation measurements in a field of up
to 12 T. At low temperature, two well-defined first order magnetic phase
transitions are found in this range of applied magnetic field (H // c): at
H_c1=7.6(3)/7.1(3) T and H_c2=13.2(1)/12.7(1) T when ramping the field up/down.
In a field above H_c2 the magnetic Bragg peaks show unusual history dependence.
In zero field T_N1=14.2(1) K separates a high temperature paramagnetic and an
intermediate incommensurate structure, while T_N2=11.1(3) K divides an
incommensurate phase from the low-temperature 4-sublattice ground state. The
ordering temperature T_N1 is found to be almost field independent, while T_N2
decreases noticeably in applied field. The magnetic phase diagram is discussed
in terms of the interactions between an applied magnetic field and the highly
frustrated magnetic structure of CuFeO_2Comment: 7 pages, 8 figures in ReVTeX. To appear in PR
Gradual pressure-induced enhancement of magnon excitations in CeCoSi
CeCoSi is an intermetallic antiferromagnet with a very unusual temperature-pressure phase diagram: at ambient pressure it orders below TN = 8.8 K, while application of hydrostatic pressure induces a new magnetically ordered phase with exceptionally high transition temperature of ∼40 K at 1.5 GPa. We studied the magnetic properties and the pressure-induced magnetic phase of CeCoSi by means of elastic and inelastic neutron scattering (INS) and heat capacity measurements. At ambient pressure CeCoSi orders into a simple commensurate AFM structure with a reduced ordered moment of only mCe = 0.37(6)μB. Specific heat and low-energy INS indicate a significant gap in the low-energy magnon excitation spectrum in the antiferromagnetic phase, with the CEF excitations located above 10 meV. Hydrostatic pressure gradually shifts the energy of the magnon band towards higher energies and the temperature dependence of the magnons measured at 1.5 GPa is consistent with the phase diagram. Moreover, the CEF excitations are also drastically modified under pressure.Fil: Nikitin, S. E.. Max Planck Institute for Chemical Physics of Solids; Alemania. Technische Universität Dresden; AlemaniaFil: Franco, Diego Gaspar. Max Planck Institute for Chemical Physics of Solids; Alemania. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro. Archivo Histórico del Centro Atómico Bariloche e Instituto Balseiro | Universidad Nacional de Cuyo. Instituto Balseiro. Archivo Histórico del Centro Atómico Bariloche e Instituto Balseiro; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Kwon, J.. Max Planck Institute for Chemical Physics of Solids; AlemaniaFil: Bewley, R.. Harwell Campus. STFC Rutherford Appleton Laboratory. ISIS Facility; Reino UnidoFil: Podlesnyak, Andrey. Oak Ridge National Laboratory. Neutron Scattering Division; Estados UnidosFil: Hoser, A.. Helmholtz-Zentrum Berlin für Materialien und Energie; AlemaniaFil: Koza, M. M.. Institute Laue Langevin; FranciaFil: Geibel, C.. Max Planck Institute for Chemical Physics of Solids; AlemaniaFil: Stockert, O.. Max Planck Institute for Chemical Physics of Solids; Alemani
Magnetization reversal driven by electron localization-delocalization crossover in the inverse spinel Co2VO4
Cytotoxicity of Bacterial Metabolic Products, including Listeriolysin O, on Leukocyte Targets
Bacterial toxins can exhibit anticancer activities. Here we investigated the anticancer effects of the listeriolysin O toxin produced by Listeria monocytogenes. We found that supernatants of Listeria monocytogenes strains (wild type, 1189, and 1190) were cytotoxic to the Jurkat cell line and human peripheral blood mononuclear cells (PBMC) in a concentration-dependent manner. The supernatant of strain 1044, not producing listeriolysin O, was inactive. The supernatants of Listeria strains were also cytotoxic toward B cells of chronic leukemia patients, with no significant differences in activities between strains. We also tested supernatants of Bacillus subtilis strains BR1-90, BR1-S, and BR1-89 producing listeriolysin O. BR1-S and BR1-89 were cytotoxic to PBMC and to Jurkat cells, the latter being more sensitive to the supernatants. BR1-90 was not hemolytic or cytotoxic to PBMC, but was cytotoxic to Jurkat cells in the concentration range of 10–30%, suggesting that listeriolysin O is selectively effective against T cells. Overall, the response of human peripheral blood mononuclear and human leukemia cell lines to bacteria supernatants containing listeriolysin O depended on the bacteria strain, target cell type, and supernatant concentration
Neutron scattering study of the field-induced soliton lattice in CuGeO
CuGeO undergoes a transition from a spin-Peierls phase to an
incommensurate phase at a critical field of T. In the
high-field phase a lattice of solitons forms, with both structural and magnetic
components, and these have been studied using neutron scattering techniques.
Our results provide direct evidence for a long-ranged magnetic soliton
structure which has both staggered and uniform magnetizations, and with
amplitudes that are broadly in accord with theoretical estimates. The magnetic
soliton width, , and the field dependence of the incommensurability,
, are found to agree well with theoretical predictions.Comment: 5 pages, 3 figure
Characterization of a new small cell lung cancer (SCLC) cell line STP54 derived from a metastatic bioptate of a combined type of SCLC with Non-SCLC component.
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