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TT: Fachverband Tiefe Temperaturen

TT 79: Correlated Electrons - Poster Session

TT 79.51: Poster

Mittwoch, 2. April 2014, 15:00–19:00, P2

Crystal growth and analysis of BaCuSi₂O₆ — •Pascal Puphal, Natalija van Well, Franz Ritter, Cornelius Krellner, and Wolf Aßmus — Physikalisches Institut, Goethe-Universität Frankfurt, Deutschland

BaCuSi₂O₆ is of interest since it has a two dimensional BEC-Phase at low temperature from 23,2 to 49,3 T. Crystal growth of this crystal is difficult, but was achieved using oxygen partial pressure or flux-method(LiBO₂). However, the system tends to glaze especially using LiBO₂ as flux. We found NaBO₂ to work as flux as well and KBO₂ to be the best. Also we could prove with an electron microscope that the flux is not incorporated in the structure. We have investigated that an alloy of platinum and gold as crucible material improves the growth since it interacts less with the material.
BaCuSi₂O₆ has a structural phase transition from tetragonal to orthorhombic, which we explore with low temperature powder diffraction, magnetic, and specific heat measurements. Furthermore, we investigated strontium substitution on the barium side, which we proved to be possible up to 30%. It leads to a reduction of the unit cell, which suppresses the structural phase transition already at 5% strontium. Calcium substitution behaves differently: it only leads to defects in the crystal, which also suppress the phase transition but with increasing calcium, it even destroys the dimer-coupling of cupper.