RB-87 NMR OF THE STRUCTURAL PHASE-TRANSITION IN RBSCN

Citation
R. Blinc et al., RB-87 NMR OF THE STRUCTURAL PHASE-TRANSITION IN RBSCN, Physical review. B, Condensed matter, 52(2), 1995, pp. 833-840
Citations number
15
Categorie Soggetti
Physics, Condensed Matter
ISSN journal
01631829
Volume
52
Issue
2
Year of publication
1995
Pages
833 - 840
Database
ISI
SICI code
0163-1829(1995)52:2<833:RNOTSP>2.0.ZU;2-R
Abstract
The second-order shifts of the Rb-87 1/2 --> - 1/2 NMR transitions hav e been measured in RbSCN above and below T-c=435 K for crystal rotatio ns around the a, b, and c axes. Whereas below T-c the Rb-87 electric-f ield gradient (EFG) and chemical shift tensors are compatible with the Rb site symmetry as given by the orthorhombic space group D-2h(ll)(Pb cm), this is not the case for the EFG data above T-c. The results show that the symmetry of the high-temperature tetragonal phase is dynamic ally broken on the Larmor frequency (10(-8) s) time scale whereas symm etry-breaking terms are averaged out on the ''site'' splitting, domain splitting, and chemical shift tenser (similar or equal to 10(-2)-10(- 3) s) time scales. Rb-87 NMR thus allows for an observation of the pha se transition in RbSCN in the ''slow motion'' regime where the high-te mperature phase is seen to consist of a large number of orthorhombic m icrodomains with lifetimes longer than 10(-7) s and shorter than 10(-3 ) s.