Low-frequency phonon dynamics, spin-lattice relaxation, and sound attenuation in crystals with incommensurate phases

2005 ◽  
Vol 50 (2) ◽  
pp. 270-277
Author(s):  
S. A. Minyukov ◽  
A. P. Levanyuk
Keyword(s):  
Low Frequency ◽  
Lattice Relaxation ◽  
Sound Attenuation ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Phonon Dynamics ◽  
Incommensurate Phases

2H and 14N NMR Studies of the Dynamics in the Incommensurate Phases of Betaine Calciumchloride Dihydrate

1995 ◽  
Vol 50 (4-5) ◽  
pp. 368-372 ◽  
Author(s):  
U. Häcker ◽  
D. Michel ◽  
K.-P. Hölzer ◽  
J. Petersson
Keyword(s):  
Low Frequency ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Relaxation Rates ◽  
Nmr Studies ◽  
Spin Lattice ◽  
Modulated Phases ◽  
Soliton Lattice ◽  
Higher Spin ◽  
Incommensurate Phases

Abstract2H and 14N NMR spin-lattice relaxation rates were measured in the structurally incommensurately (IC) modulated phases of deuterated and undeuterated betaine calciumchloride dihydrate, respectively. The results are related to the elementary excitations of these phases. The presence of low-frequency phase fluctuations of the modulation wave leads to higher spin-lattice relaxation rates compared with the high-temperature normal phase and the commensurate (C) phases. The corresponding "phason" contributions are found to be nearly constant in the whole IC phases. In the IC phases near the transitions to the C phases the relaxation rates decrease due to the formation of the soliton lattice. This interpretation is in agreement with the results of previous dielectric measurements

Calculation of NQR v's and T1-1' s being proportional to T4 and T5 , respectively

1990 ◽  
Vol 45 (3-4) ◽  
pp. 536-540
Author(s):  
Mariusz Máckowiak ◽  
Costas Dimitropoulos
Keyword(s):  
Temperature Dependence ◽  
Relaxation Rate ◽  
Spin System ◽  
Low Frequency ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Lattice Vibrations ◽  
Spin Lattice ◽  
Simplifying Assumptions ◽  
The One

Abstract The second-order Raman phonon process for a multilevel spin system is shown to give a quadru-polar spin-lattice relaxation rate T1-1varying as T5 at very low temperatures. This relaxation rate for quadrupole spins is similar to the one discussed for a paramagnetic spin system having a multilevel ground state. The temperature dependence of T1 is discussed on the basis of some simplifying assumptions about the nature of the lattice vibrations in the Debye approximation. This type of relaxation process has been observed below 20 K in tetramethylammonium hydrogen bis-trichloroacetate for the 35Cl T1-1 . Below 20 K the NQR frequency in the same crystal reveals a T4 temperature dependence due to the induced modulations of the vibrational and librational coordinates by the low-frequency acoustic phonons.

Time Domain Zero Field NMR and NQR

1986 ◽  
Vol 41 (1-2) ◽  
pp. 440-444 ◽  
Author(s):  
A. Bielecki ◽  
D. B. Zax ◽  
A. M. Thayer ◽  
J. M. Millar ◽  
A. Pines
Keyword(s):  
Time Domain ◽  
Relaxation Times ◽  
Low Frequency ◽  
High Sensitivity ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Zero Field ◽  
Spin Lattice ◽  
Field Cycling ◽  
The Time Domain

Field cycling methods are described for the time domain measurement of nuclear quadrupolar and dipolar spectra in zero applied field. Since these techniques do not involve irradiation in zero field, they offer significant advantages in terms of resolution, sensitivity at low frequency, and the accessible range of spin lattice relaxation times. Sample data are shown which illustrate the high sensitivity and resolution attainable. Comparison is made to other field cycling methods, and an outline of basic instrumental requirements is given.

Low Frequency Dynamics of Confined Proteins

2003 ◽  
Vol 790 ◽  
Author(s):  
Jean-Pierre Korb ◽  
Robert G. Bryant
Keyword(s):  
Spatial Distribution ◽  
Protein Structure ◽  
Low Frequency ◽  
Lattice Relaxation ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Low Frequencies ◽  
Spin Lattice ◽  
Raman Process ◽  
Hydrated Proteins

ABSTRACTWe present the frequency dependence of the proton spin-lattice relaxation rate 1/T1 in variously hydrated proteins. We present also the case of proteins confined in heavily hydrated gels where the rotation has been immobilized. The relaxation efficiency increases according to a power law at low frequencies. The temperature dependence of the protein protons T1 demonstrates that relaxation results from a direct spin-phonon process instead of a Raman process at temperatures above 273K. We propose a theory that accounts for experiments and depends on the dynamical distribution of states, the localization of the disturbances along and transverse to the peptide chains, and the spatial distribution of hydrogen in the structure. In hydrated and confined proteins, the motions of the backbone that dominate the relaxation process are transverse rather than along the peptide chain. We show that the protein structure adjusts to hydration from the lyophilized state to the fully hydrated state in small increment steps.

scholarly journals Magnetic Properties of the Doped Two-Dimensional Antiferromagnet

2003 ◽  
Vol 17 (10n12) ◽  
pp. 433-440 ◽  
Author(s):  
A. Sherman ◽  
M. Schreiber
Keyword(s):  
Magnetic Properties ◽  
Hole Concentration ◽  
Low Frequency ◽  
Lattice Relaxation ◽  
Spin Correlation ◽  
The Self ◽  
Spin Lattice Relaxation ◽  
Two Dimensional ◽  
Spin Lattice ◽  
Consistent Solution

The variety of the normal-state magnetic properties of cuprate high-Tc superconductors is interpreted based on the self-consistent solution of the self-energy equations for the two-dimensional t-J model. The observed variations of the spin correlation length with the hole concentration x, of the spin susceptibility with x and temperature T and the scaling of the static uniform susceptibility are well reproduced by the calculated results. The nonmonotonic temperature dependence of the Cu spin-lattice relaxation rate is connected with two competing tendencies in the low-frequency susceptibility: its temperature decrease due to the increasing spin gap and the growth of the susceptibility in this frequency region with the temperature broadening of the maximum in the susceptibility.

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