Temperature dependent decay of a metastable state of systems with large impurity-lattice relaxation (CdF2 : In)

2008 ◽  
pp. 150-154
Author(s):  
U. Ogonowska
Keyword(s):  
Metastable State ◽  
Lattice Relaxation ◽  
Temperature Dependent

DYNAMICS OF THE LOW TEMPERATURE GLASS-LIKE PHASE IN MANGANITES

2003 ◽  
Vol 17 (04n06) ◽  
pp. 842-847
Author(s):  
C. CASTELLANO ◽  
F. CORDERO ◽  
R. CANTELLI ◽  
M. FERRETTI
Keyword(s):  
Distribution Function ◽  
Phase Transitions ◽  
Quantitative Analysis ◽  
Low Temperature ◽  
Imaginary Part ◽  
Lattice Relaxation ◽  
Relaxation Processes ◽  
Temperature Dependent ◽  
Energy Barriers ◽  
Nanostructured State

We report anelastic spectroscopy measurements of La 1-x Ca x MnO 3 performed in order to better characterize the nature of the phase transitions and microscopic lattice relaxation processes present in these materials. A peak in the imaginary part of the elastic susceptibility presents a behaviour typical of inhomogeneous and glass-like systems. We have performed a quantitative analysis calculating the temperature dependent distribution function of the energy barriers of the fluctuations characterizing this nanostructured state.

1HNMR Study on the Motion of NH4+ in Ferroelectric NH4H(ClH2CCOO)2 and Mixed (NH4)1-xRbxH(ClH2CCOO)2 (x = 0.15)

2002 ◽  
Vol 57 (11) ◽  
pp. 883-887 ◽  
Author(s):  
M. Zdanowska-Fra̡czek ◽  
A. Kozaka ◽  
R. Jakubasb ◽  
J. Wa̡sickia ◽  
R. Utrechta
Keyword(s):  
Relaxation Time ◽  
Group Dynamics ◽  
Nmr Relaxation ◽  
Activation Parameters ◽  
Lattice Relaxation ◽  
Relaxation Mechanism ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Temperature Dependent ◽  
Spin Lattice

Temperature-dependent proton NMR relaxation time measurements have been performed at 60 MHz in order to study the NH4+ dynamics in ferroelectric NH4H(ClH2CCOO)2 and mixed Rbx(NH4)1-x(ClH2CCOO)2, where x = 0.15. The data indicate that the dominant relaxation mechanism for the NMR spin-lattice relaxation time T 1 in both crystals involves simultaneous NH4 group reorientation about their C2 and C3 symmetry axis in the paraelectric phase. Details of the NH4+reorientation have been inferred from analysis of temperature dependence of T1 assuming the Watton model. The activation parameters of the motionshave been determined.It has been found that the substitution of Rb does not change the activation parameters of the NH4 group dynamics.

A 35CL NQR Spin-Lattice Relaxation Study on the Motion of D4h Anions in [C(NH2)3]2PdCl4, [C(NH2)3]2PtCl4, and [C(NH2)3]AuCl4

1986 ◽  
Vol 41 (1-2) ◽  
pp. 416-420
Author(s):  
Yoshihiro Furukawa ◽  
Daiyu Nakamura
Keyword(s):  
Relaxation Times ◽  
Sharp Decrease ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Temperature Dependent ◽  
Spin Lattice ◽  
35Cl Nqr ◽  
The One ◽  
Increasing Temperature ◽  
Complex Anions

The temperature dependence of 35Cl NQR spin-lattice relaxation times T1ClQ was observed for the crystal of the title complexes. For the Pd(II) and Pt(II) complexes, the log T1ClQ vs. 103 T-1 curves having gentle positive gradients at lower temperatures decreased sharply with increasing temperature from ca. 150 and ca. 130 K, respectively. This sharp decrease of T1ClQ can be explained by the C4 reorientation of the D4h complex anions with the activation energy Ea of 34 kJ mol-1 for the former and 29 kJ mol-1 for the latter complex. These values agree well with those estimated from 1H T1 showing temperature dependent dipolar-quadrupolar cross relaxation. For the Au(III) salt, two of four 35Cl NQR lines showed a sharp decrease in T1ClQ from ca. 270 K, suggesting the onset of the C4 reorientation of the one kind crystallographically equivalent anions with Ea of 67 kJ mol-1.

Proton Relaxation in Various Copper (II) Complexes and Determination of the Singlet-Triplet Separation

1980 ◽  
Vol 35 (1) ◽  
pp. 92-97 ◽  
Author(s):  
H. D. Jannek ◽  
W. Midler-Warmuth
Keyword(s):  
Copper Complexes ◽  
Lattice Relaxation ◽  
Magnetic Behaviour ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Proton Relaxation ◽  
Relaxation Rates ◽  
Temperature Dependent ◽  
Spin Lattice

Abstract Proton spin-lattice relaxation rates have been measured at 30 MHz as a function of temperature for a large number of dimeric copper complexes with the ligands 8-hydroxyquinoline, pyridine-N-oxide, methyl and dimethyl pyridine-N-oxide, and quinoline-N-oxide. Two carboxylates and adducts of several complexes with various solvents have also been studied. In contrast to some compounds with a normal magnetic behaviour, for most complexes a temperature dependent relaxation has been observed which agrees well with the concept of a weak antiferromagnetic interaction between the two Cu2+ ions. The singlet-triplet separations or exchange integrals have been determined.

scholarly journals Vibronic Effects in Mossbauer Spectra: The 57Fe Quadrupole Splitting in FeCO3

1978 ◽  
Vol 31 (5) ◽  
pp. 397 ◽  
Author(s):  
DC Price
Keyword(s):  
Quadrupole Splitting ◽  
Lattice Relaxation ◽  
Vibronic Coupling ◽  
Spin Lattice Relaxation ◽  
Relaxation Rates ◽  
Temperature Dependent ◽  
Spin Lattice ◽  
Symmetry Properties ◽  
Coupling Parameters ◽  
Magnetic Ions

The methods developed by Orbach and coworkers for calculating spin-lattice relaxation rates have been generalized to enable calculation of the effects of vibronic admixture between low-lying electronic states on observables, such as the Mossbauer quadrupole splitting, associated with magnetic ions in crystals. Emphasis is placed on the need to take proper account of the symmetry properties of the phonons until a late stage in the calculation. Application is made to the temperature dependence of the 57Fe quadrupole splitting in FeC03 , and it is concluded that, in general, vibronic coupling effects must be considered before static splitting parameters are extracted from experimental data relating to the temperature-dependent populations of electronic levels. The superposition model of the crystal field is employed to estimate the vibronic coupling parameters.

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