164 research outputs found
Temperature Dependence of the Cu(2) NQR Line Width in YBaCuO
Systematic measurements of the Cu(2) NQR line width were performed in
underdoped YBaCuO samples over the temperature range 4.2 K
K. It was shown that the copper NQR line width monotonically increases
upon lowering temperature in the below-critical region, resembling temperature
behavior of the superconducting gap. The observed dependence is explained by
the fact that the energy of a condensate of sliding charge-current states of
the charge-density-wave type depends on the phase of order parameter.
Calculations show that this dependence appears only at . Quantitative
estimates of the line broadening at agree with the measurement results.Comment: 4 pages, 2 figure
Electronic structure and indirect spin-spin interactions in bournonite (CuPbSbS3) according to antimony nuclear quadrupole resonance
A complex sulfide CuPbSbS3 (bournonite) has been studied by the nuclear quadrupole resonance on 121,123Sb. The temperature dependences of the spectroscopic and relaxation parameters in the temperature range of 10-295 K have been obtained. The crystallochemical features of the environment of the two non-equivalent Sb positions in the unit cell have been revealed from the nuclear quadrupole resonance spectra. The existence of the lattice vibrations with the frequency ω = 110 cm-1 has been demonstrated on the basis of the temperature dependence of the nuclear quadrupole resonance frequencies. Slow beats have been observed on the decay curve of the spin echo signal. Experimental data have been analyzed in order to reveal the existence of the indirect spin-spin interactions involving Sb atoms. The indirect spin-spin coupling constant has been estimated as J = 2.5 ± 0.5 kHz. © 2013 Pleiades Publishing, Ltd
E.K. Zavoiskii and NMR: Analysis of laboratory notebooks and rerun of experiments
© 2015 AIP Publishing LLC. An analysis of the laboratory notebooks of E. K. Zavoiskii, the discoverer of electron paramagnetic resonance, shows that in 1941 he began trying to observe NMR of various nuclei in condensed matter. A rerun of his NMR experiments shows that the sensitivity of the "grid current" method that he developed was adequate for reliable detection of NMR of protons in water solutions of paramagnetic salts. The reason for the poor reproducibility of Zavoiskii's NMR experiments was insufficient the homogeneity of the magnetic field of the electromagnets he used
NMR study of the low temperature magnetic excitations in RBa2(Cu1 - YNiy)3O6 (R = Y, Tm)
Cu(1) NQR, Cu(2) Zero Field NMR and Tm NMR spin-lattice relaxation data have been found quite different in the two AF states of the 123 compounds. In the usual AF-I phase of the pure compounds T1 is short and nearly T-independent at low T. With Ni or Co substitutions in the above by about 2% concentration, the Cu(2) bilayers are ordered ferromagnetically with respect to each other (AF-II phase), which is evidenced by a splitting of the Cu(1) NQR. In this case, T1 -1 is much smaller and exhibits a strong T dependence, which might be associated with a 5 K gap in the magnetic excitation spectrum. We suggest that magnetic defects apparently unavoidable on the Cu(1) sites govern the spin dynamics. While they are frustrated in the "pure samples", they are not in the AF-II phase, which suppresses partly their spin fluctuations
A novel data on Ag5SbS4 and CuPbSbS3 probed by antimony NQR spectroscopy
Investigations of Sb-based chalcogenides, stephanite Ag5SbS 4 and bournonite CuPbSbS 3, have been performed by 121,123Sb nuclear quadrupole resonance (NQR). In stephanite a phase transition at 140 K and internal diffusion motions with an activation energy of 0.29 eV have been experimentally detected. The analysis of experimental results for bournonite revealed two crystal-chemical positions of Sb in the unit cell with distinct local symmetry. The NQR frequencies ν and line-widths Δν data indicate that Sb(A)S3 complex has almost axial symmetry, but Sb(B)S 3 complex is substantially distorted
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