N14nuclear-quadrupole-resonance study of the structural phase transitions inNH4SCN

1990 ◽  
Vol 42 (13) ◽  
pp. 8125-8132 ◽  
Author(s):  
R. Blinc ◽  
J. Seliger ◽  
V. Žagar ◽  
T. Apih ◽  
J. Dolinšek ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Structural Phase ◽  
Structural Phase Transitions ◽  
Quadrupole Resonance

NQR study of the structural phase transitions in a system with reduced effective dimensionality: K2ReCl6

1983 ◽  
Vol 61 (10) ◽  
pp. 1374-1381 ◽  
Author(s):  
Marie D'Iorio ◽  
Robin L. Armstrong
Keyword(s):  
Fourier Transform ◽  
Phase Transitions ◽  
Hydrostatic Pressure ◽  
Magnetic Resonance ◽  
Structural Phase ◽  
Nonlinear Phenomena ◽  
Structural Phase Transitions ◽  
Quadrupole Resonance ◽  
Nuclear Quadrupole ◽  
Effective Dimensionality

Chlorine 35 nuclear quadrupole resonance (NQR) frequency and lineshape data, obtained with a Fourier transform magnetic resonance spectrometer, are presented for the antifluorite crystal K2ReCl6. In the temperature range investigated, 85 to 130 K, two structural phase transitions occur which reduce the crystal symmetry from cubic to tetragonal to monoclinic. The variation of the NQR spectrum with temperature and with hydrostatic pressure up to 2.64 kbar is documented. The structure of the spectrum and the intensity distribution within it are unexpected from previous studies of antifluorite systems. An explanation of the results is given which is based on recent discussions of nonlinear phenomena at phase transitions in crystals exhibiting reduced effective dimensionality.

Neutron-diffraction study of the structural phase transitions in the antifluorite K2PtBr6

1985 ◽  
Vol 63 (7) ◽  
pp. 988-996 ◽  
Author(s):  
Robin L. Armstrong ◽  
Rose M. Morra ◽  
Brian M. Powell
Keyword(s):  
Phase Transitions ◽  
Nuclear Quadrupole Resonance ◽  
Goodness Of Fit ◽  
Structural Phase ◽  
Spectral Characteristics ◽  
Neutron Diffraction Study ◽  
Structural Phase Transitions ◽  
Quadrupole Resonance ◽  
Nuclear Quadrupole

Neutron-powder-diffraction profiles are reported for the antifluorite K2PtBr6 at temperatures of 296, 160, 141, and 120 K. Bromine nuclear-quadrupole-resonance measurements have shown that each of these temperatures corresponds to a different crystal structure and have provided information on the most probable structures. A variety of structural models with symmetries obtained from a group theoretical classification of structural phase transitions are fitted to the diffraction data. A comparison of goodness-of-fit parameters for the models considered at each temperature allows the space group of each phase to be identified. The results provide (i) a definitive test of the validity of a classification scheme proposed for nuclear-quadrupole-resonance spectral characteristics, and (ii) support for the proposition that the allowable, continuous distortions of a crystal are given by the nondisruptive criterion rather than the more restrictive group–subgroup criterion.

Phonons and magnons under the sequential structural phase transitions in La2NiO4

1991 ◽  
Vol 185-189 ◽  
pp. 895-896 ◽  
Author(s):  
S. Sugai ◽  
S. Hosoya ◽  
T. Kajitani ◽  
T. Fukuda ◽  
S. Onodera
Keyword(s):  
Phase Transitions ◽  
Structural Phase ◽  
Structural Phase Transitions
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