A1 Refereed original research article in a scientific journal
Deuteron NMR study of the diverse mobility of the ammonium ions in the ordered phase of (ND4)(2)PtCl4
Authors: Lalowicz ZT, Punkkinen M, Olejniczak Z, Birczytiski A, Haeberlen U
Publisher: ACADEMIC PRESS INC ELSEVIER SCIENCE
Publication year: 2002
Journal:: Solid State Nuclear Magnetic Resonance
Journal name in source: SOLID STATE NUCLEAR MAGNETIC RESONANCE
Journal acronym: SOLID STATE NUCL MAG
Volume: 22
Issue: 2-3
First page : 373
Last page: 393
Number of pages: 21
ISSN: 0926-2040
DOI: https://doi.org/10.1006/snmr.2002.0076
Abstract
A detailed description of the diverse mobility of the ND4+ ions in the low-temperature ordered phase of (ND4)(2)PtCl4 is developed on the basis of single-crystal deuteron NMR spectra and site-selective T measurements. The ordered phase of (ND4)(2)PtCl4 consists of two kinds of domains in which the orientation of the ND4+ tetrahedra differs by a 90 rotation about an axis which otherwise is a two-fold symmetry axis of the tetrahedra. Inside the domains, the NDQ ions do not reorient at low temperatures. The domains are separated by domain walls which contain, according to the deuteron NMR spectra, about 10% of all ND4+ ions. These ions are highly mobile even at 10 K. On rising the temperature, the thickness of the domain walls increases, that is, the ions in more and more layers become mobile. Moreover, we provide evidence for fluctuations of the locations of the domain walls. The central resonance of the domain-wall ions shows a complicated structure below 36 K. On the basis of a tunnelling hypothesis we make an attempt to account for this structure. There are indications that the tunnelling process is incoherent. (C) 2002 Elsevier Science (USA).
A detailed description of the diverse mobility of the ND4+ ions in the low-temperature ordered phase of (ND4)(2)PtCl4 is developed on the basis of single-crystal deuteron NMR spectra and site-selective T measurements. The ordered phase of (ND4)(2)PtCl4 consists of two kinds of domains in which the orientation of the ND4+ tetrahedra differs by a 90 rotation about an axis which otherwise is a two-fold symmetry axis of the tetrahedra. Inside the domains, the NDQ ions do not reorient at low temperatures. The domains are separated by domain walls which contain, according to the deuteron NMR spectra, about 10% of all ND4+ ions. These ions are highly mobile even at 10 K. On rising the temperature, the thickness of the domain walls increases, that is, the ions in more and more layers become mobile. Moreover, we provide evidence for fluctuations of the locations of the domain walls. The central resonance of the domain-wall ions shows a complicated structure below 36 K. On the basis of a tunnelling hypothesis we make an attempt to account for this structure. There are indications that the tunnelling process is incoherent. (C) 2002 Elsevier Science (USA).
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