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Study of NH 4 motion in some antiferroelectric crystals by inelastic scattering of cold neutrons
Author(s) -
Dimic V.,
Osredkar M.,
Slak J.,
Kandušsar A.
Publication year - 1973
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2220590213
Subject(s) - inelastic neutron scattering , deuterium , inelastic scattering , antiferroelectricity , chemistry , neutron scattering , neutron , quasielastic neutron scattering , spectral line , scattering , analytical chemistry (journal) , atomic physics , nuclear magnetic resonance , materials science , dielectric , physics , optics , ferroelectricity , nuclear physics , optoelectronics , chromatography , astronomy
The spectra of the inelastic scattering of cold neutrons by antiferroelectric NH 4 H 2 PO 4 , NH 4 H 2 AsO 4 , and (NH 4 ) 2 H 3 IO 6 have been measured above and below their transition point, using a rotating crystal spectrometer together with a cold source. The low temperature neutron measurements show very little change as compared with the room temperature results. The torsional bands are narrow in both phases. The broadening of the bands is inversely related to the hindrance, and therefore the measurements suggest that the rotation of the NH + 4 ion is strongly hindered, which is supported by the angular distribution of elastic scattering. The deuteron magnetic resonance of ND 4 D 2 AsO 4 indicates that in addition to rotational motion of the ND 4 group this group might oscillate in the paraelectric phase. The oscillational mode condenses at T c . In order to check the assignments obtained from the inelastic neutron scattering studies the ir absorption spectra of NH 4 H 2 PO 4 , NH 4 H 2 AsO 4 , and (NH 4 ) 2 H 3 IO 6 and their deuterated analogues were measured at room temperature.