226 research outputs found
Electrical resistivity and tunneling anomalies in CeCuAs2
The compound CeCuAs2 is found to exhibit negative temperature (T) coefficient
of electrical resistivity (rho) under ambient pressure conditions in the entire
T-range of investigation (45 mK to 300 K), even in the presence of high
magnetic fields. Preliminary tunneling spectroscopic measurements indicate the
existence of a psuedo-gap at least at low temperatures, thereby implying that
this compound could be classified as a Kondo semi-conductor, though rho(T)
interestingly is not found to be of an activated type.Comment: To appear in the proceedings of SCES200
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Spin-glass state and reversed magnetic anisotropy induced by Cr doping in the Kitaev magnet α-RuCl3
Magnetic properties of the substitution series Ru1-xCrxCl3 were investigated to determine the evolution from the anisotropic Kitaev magnet α-RuCl3 with Jeff=1/2 magnetic Ru3+ ions to the isotropic Heisenberg magnet CrCl3 with S=3/2 magnetic Cr3+ ions. Magnetization measurements on single crystals revealed a reversal of the magnetic anisotropy under doping, which we argue to arise from the competition between anisotropic Kitaev and off-diagonal interactions on the Ru-Ru links and approximately isotropic Cr-Ru and isotropic Cr-Cr interactions. In addition, combined magnetization, ac susceptibility, and specific-heat measurements clearly show the destabilization of the long-range magnetic order of α-RuCl3 in favor of a spin-glass state of Ru1-xCrxCl3 for a low doping of x≤0.1. The corresponding freezing temperature as a function of Cr content shows a broad maximum around x ≤ 0.45
Dilution of the magnetic lattice in the Kitaev candidate α-RuCl<sub>3</sub> by Rh<sup>3+</sup> doping
Dilution of the magnetic lattice in the Kitaev candidate -RuCl by Rh doping
Magnetic dilution of a well-established Kitaev candidate system is realized
in the substitutional RuRhCl series (). Optimized
syntheses protocols yield uniformly-doped single crystals and polycrystalline
powders that are isostructural to the parental -RuCl as per X-ray
diffraction. The Rh content is accurately determined by the quantitative
energy-dispersive X-ray spectroscopy technique with standards. We determine the
magnetic phase diagram of RuRhCl for in-plane magnetic fields
from magnetization and specific-heat measurements as a function of and
stacking periodicity, and identify the suppression of the magnetic order at towards a disordered phase, which does not show any clear
signature of freezing into a spin glass. Comparing with previous studies on the
substitution series RuIrCl, we propose that chemical pressure
would contribute to the suppression of magnetic order especially in
RuIrCl and that the zigzag magnetic ground state appears to be
relatively robust with respect to the dilution of the
Kitaev----Heisenberg magnetic lattice. We also discovered a slight
dependence of the magnetic properties on thermal cycling, which would be due to
an incomplete structural transition
Crystal Growth and Structure Determination of Pigment Orange 82
The crystal structure of the important industrial orangepigment PO82, major part of the BASF Colors amp; Effects productSicopal Orange K L 2430, was solved from combined X ray singlecrystal, X ray and neutron powder diffraction,119Sn Mössbauer spec troscopy, transmission electron microscopy, electron diffraction, andchemical analyses. The structure contains Keggin type clusters com posed of four [M3O13] trimers consisting each of three MO6 octahedra that share edges and one common oxygen atom connecting the trimersto the central ZnO4tetrahedron. The octahedrally coordinated metalatom position is mixed occupied by Ti4 ,Sn4 , and Zn2 . AdjacentKeggin clusters share vertices and are further interconnected to fourZnO4tetrahedra. This framework of interconnectedMO6octahedra andZnO4tetrahedra contains channels along [110], in which the Sn2 cat ions are locate
First broadband characterization and redshift determination of the VHE blazar MAGIC J2001+439
We aim to characterize the broadband emission from 2FGL J2001.1+4352, which
has been associated with the unknown-redshift blazar MG4 J200112+4352. Based on
its gamma-ray spectral properties, it was identified as a potential very high
energy (VHE; E > 100 GeV) gamma-ray emitter. The source was observed with MAGIC
first in 2009 and later in 2010 within a multi-instrument observation campaign.
The MAGIC observations yielded 14.8 hours of good quality stereoscopic data.
The object was monitored at radio, optical and gamma-ray energies during the
years 2010 and 2011. The source, named MAGIC J2001+439, is detected for the
first time at VHE with MAGIC at a statistical significance of 6.3 {\sigma} (E >
70 GeV) during a 1.3-hour long observation on 2010 July 16. The
multi-instrument observations show variability in all energy bands with the
highest amplitude of variability in the X-ray and VHE bands. We also organized
deep imaging optical observations with the Nordic Optical Telescope in 2013 to
determine the source redshift. We determine for the first time the redshift of
this BL Lac object through the measurement of its host galaxy during low blazar
activity. Using the observational evidence that the luminosities of BL Lac host
galaxies are confined to a relatively narrow range, we obtain z = 0.18 +/-
0.04. Additionally, we use the Fermi-LAT and MAGIC gamma-ray spectra to provide
an independent redshift estimation, z = 0.17 +/- 0.10. Using the former (more
accurate) redshift value, we adequately describe the broadband emission with a
one-zone SSC model for different activity states and interpret the few-day
timescale variability as produced by changes in the high-energy component of
the electron energy distribution.Comment: 17 pages, 15 figures, Accepted for publication in A&
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