Regensburg 2019 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 50: Poster Session: Correlated Electrons 2
TT 50.12: Poster
Mittwoch, 3. April 2019, 15:00–18:30, Poster D
Thermal expansion studies on the quantum-spin-liquid candidate Ca10Cr7O28 — •C. Thurn1, S. Thallapaka1, U. Tutsch1, C. Balz2,3,4, B. Lake3,4, and M. Lang1 — 1PI, Goethe Uni, Frankfurt/M., SFB/TR49, Germany — 2Oak Ridge National Laboratory, USA — 3HZ Berlin, Germany — 4TU Berlin, Germany
In a quantum spin liquid (QSL) strong zero-point fluctuations prevent long-range magnetic order down to lowest temperatures [1]. A common approach for a realization of a QSL is via the help of magnetic frustration of geometric origin. In Ca10Cr7O28 magnetic S=1/2 Cr5+-ions are arranged in distorted kagome bilayers formed by two inequivalent planes of corner-sharing equilateral triangles: an upper triangle coupled ferromagnetically (FM) and a lower triangle coupled antiferromagnetically (AFM) with the FM coupling being dominant. A weak FM inter-plane interaction prevents each plane from reaching its ground state leading to frustration. Previous studies fail to detect any hints of long-range magnetic order down to 19 mK and found persistent spin dynamics down to lowest temperatures [2,3]. Here we present studies of the thermal expansion α and the specific heat C from 1.7 K down to 50 mK for various magnetic fields. For both quantities we find a kink-like anomaly around 0.5 K, indicative of a crossover rather than a phase transition. Measurements of α in low fields reveal a broadening of this feature accompanied by a shift to higher temperatures upon increasing the field, suggesting that FM correlations are at the origin of this feature.
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