46 research outputs found
Synthesis of sodium cobaltate NaCoO single crystals with controlled Na ordering
In this study, we synthesized single crystals of NaCoO with
using the optical floating zone technique. A thorough
electrochemical treatment of the samples permitted us to control the
de-intercalation of Na to obtain single crystal samples of stable Na ordered
phases with . Comparisons of the bulk magnetic properties with those
observed in the Na ordered powder samples confirmed the high quality of these
single crystal phases. The ab plane resistivity was measured for the Na ordered
samples and it was quite reproducible for different sample batches. The data
were analogous to those found in previous initial experimental studies on
single crystals, but the lower residual resistivity and sharper
anti-ferromagnetic transitions determined for our samples confirmed their
higher quality.Comment: 15 pages, 7 figure
Complex magnetic differentiation of cobalts in NaCoO with 22K N\'eel temperature
Single crystals of sodium cobaltates NaCoO with
were grown by the floating zone technique. Using electrochemical Na
de-intercalation method we reduced the sodium content in the as-grown crystals
down to pure phase with 22 K N\'eel temperature and . The
Co NMR study in the paramagnetic state of the K phase
permitted us to evidence that at least 6 Co sites are differentiated. They
could be separated by their magnetic behaviour into three types: a single site
with cobalt close to non-magnetic Co, two sites with the most magnetic
cobalts in the system, and the remaining three sites displaying an intermediate
behaviour. This unusual magnetic differentiation calls for more detailed NMR
experiments on our well characterized samples.Comment: 5 pages, 4 figures, submitted to JETP Let
Magnetic and spectral properties of multi-sublattice oxides SrY2O4:Er3+ and SrEr2O4
SrEr2O4 is a geometrically frustrated magnet which demonstrates rather
unusual properties at low temperatures including a coexistence of long- and
short-range magnetic order, characterized by two different propagation vectors.
In the present work, the effects of crystal fields (CF) in this compound
containing four magnetically inequivalent erbium sublattices are investigated
experimentally and theoretically. We combine the measurements of the CF levels
of the Er3+ ions made on a powder sample of SrEr2O4 using neutron spectroscopy
with site-selective optical and electron paramagnetic resonance measurements
performed on single crystal samples of the lightly Er-doped nonmagnetic
analogue, SrY2O4. Two sets of CF parameters corresponding to the Er3+ ions at
the crystallographically inequivalent lattice sites are derived which fit all
the available experimental data well, including the magnetization and dc
susceptibility data for both lightly doped and concentrated samples.Comment: 14 pages, 9 figure
Interplay between strong correlations and electronic topology in the underlying kagome lattice of Na2/3CoO2
Electronic topology in metallic kagome compounds is under intense scrutiny.
We present transport experiments in Na2/3CoO2 in which the Na order
differentiates a Co kagome sub-lattice in the triangular CoO2 layers. Hall and
magnetoresistance (MR) data under high fields give evidence for the coexistence
of light and heavy carriers. At low temperatures, the dominant light carrier
conductivity at zero field is suppressed by a B-linear MR suggesting Dirac like
quasiparticles. Lifshitz transitions induced at large B and T unveil the lower
mobility carriers. They display a negative B^2 MR due to scattering from
magnetic moments likely pertaining to a flat band. We underline an analogy with
heavy Fermion physics.Comment: Title and discussion changed after review. More technical details
have been added in the Supplementary Materials. Published as a letter in
Phys. Rev. B (Phys. Rev. B 104, L201103). 4 figures in the Main text + 7
figures in the Supplemental Material
Magnetic and Mössbauer effect studies of ZnO thin film implanted with iron ions to high fluence
© Published under licence by IOP Publishing Ltd.We present the results of magnetic and Mössbauer effect studies of zinc oxide thin film obtained by RF magnetron sputtering and implanted with 40 keV iron ions to a fluence of 1.5•1017 ion/cm2. As-implanted and post-annealed sample shows ferromagnetic properties at room temperature and consists of paramagnetic and ferromagnetic phases according to Mössbauer spectroscopy
Double-loop hysteresis of multisite dilute Sr(YDy)O single crystal Kramers paramagnets: electron-phonon interaction, quantum tunneling and cross-relaxation
Experimental and theoretical studies of the dynamic magnetization in swept
magnetic fields of the orthorhombic SrYO single-crystals doped with the
Dy Kramers ions (0.01 and 0.5 at.%) with natural abundances of even and
odd Dy isotopes are presented. Impurity ions substitute for Y ions at
two nonequivalent crystallographic sites with the same local symmetry but
strongly different crystal fields. Well pronounced double-loop hysteresis is
observed at temperatures 2, 4, 5 and 6 K for sweeping rates of 5 and 1 mT/s.
The microscopic model of spectral, magnetic and kinetic properties of Dy
ions is developed based on the results of EPR, site selective optical spectra
and magnetic relaxation measurements. The derived approach to the dynamic
magnetization in the sweeping field based on the numerical solution of
generalized master equations with time-dependent transition probabilities
induced by the electron-phonon interaction, quantum tunneling and
cross-relaxation allowed us to reproduce successfully the evolution of the
hysteresis loop shape with temperature, sweeping rate and concentration of
paramagnetic ions.Comment: 11 pages, 6 figures, 2 tables, 52 reference
Thermograms of High-Frequency Capacitive Discharge Between Solid and Liquid Electrodes
© 2018, Pleiades Publishing, Inc. Abstract: We present the experimental results on thermograms and plots of temperature distributions along the streamer and spark discharges in a high-frequency capacitive field between solid and liquid electrodes for different electrode geometries