Regensburg 2000 – scientific programme
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DF: Dielektrische Festkörper
DF 7: Poster
DF 7.7: Poster
Thursday, March 30, 2000, 09:30–13:00, C
MAGNETIC RESONANCE STUDIES OF THE FERROELECTRIC ORDER-DISORDER TRANSITION IN DIMETHYLAMMONIUM ALUMINIM SULFATE (DMAAS) — •Georg Voelkel1, Naaman Alsabbagh1, Rolf Boettcher1, Dieter Michel1, Zbigniew Czapla2, and Julek Furtak2 — 1University of Leipzig, Faculty of Physiscs and Geosciences, Linnestr. 5, D-04103 Leipzig, Germany — 2University of Wroclaw, Institute of Experimental Physics, Maxa Borna 9, PL-50204 Wroclaw, Poland
Electron paramagnetic resonance (EPR) investigations of the ordering behavior in single crystals of dimethylammonium aluminum sulfate hexahydrate (DMAAS)1,2 are presented at the transition from the ferroelastic to the ferroelectric phase. The measurements in chromium doped DMAAS show that the Cr3+ probe substitutes aluminum sites. The paper gives information about the order-disorder behavior of DMA groups. The presented EPR results are qualitativly different from previous magnetic resonance studies in order-disorder systems with respect to the capability to measure the order parameter directly and quantitatively. The EPR measurements confirm the order-disorder character of the ferroelectric phase transition at 151 K on a microscopic level and give information about the local order parameter and the critical dynamics of the dimethylammonium reorientation.