Hamburg 2001 – wissenschaftliches Programm
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DF: Dielektrische Festkörper
DF 6: Poster
DF 6.5: Poster
Mittwoch, 28. März 2001, 14:30–18:00, Foyer S3
EPR Studies of the Low-Temperature Phase of Chromium Doped Dimethylammonium Gallium Sulfate Hexahydrate (DMAGaS) — •Georg Völkel1, Rolf Böttcher1, Dieter Michel1, and Zbigniew Czapla2 — 1Faculty of Physics and Geosciences, University of Leipzig, Linnestr. 5, D-04103 Leipzig, Germany — 2Institute of Experimental Physics, University of Wroclaw, Maxa Borna 9, PL-50204 Wroclaw, Poland
Dimethylammonium gallium sulfate hexahydrate (DMAGaS) (CH3)2NH2Ga(SO4)2*6H2O and dimethylammonium aluminum sulfate hexahydrate (DMAAS) are ferroelastic and isomorphous at room temperature. They both exhibit an order-disorder type transition into a ferroelectric phase but only DMAGaS shows a further first-order transition into a low temperature non-ferroelectric phase. The nature of the low-temperature phase is not yet fully understood. We report on the first electron paramagnetic resonance (EPR) measurements of chromium doped DMAGaS performed from room temperature down to liquid helium temperature. The EPR spectroscopy opens a very interesting opportunity to study the peculiar reorientation order of the polar DMA units in DMAGaS on a microscopic level. The investigations give strong indication that DMAGaS undergoes at the transition temperature TC2 = 116 K first a transition into a modulated intermediate phase until then at T* = 64 K an antiferroelectrically ordered structure is formed with an at least doubled unit cell.
Supported by grant BO 1080/7-1 of the Deutsche Forschungsgemeinschaft.