Regensburg 2010 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 10: Measuring Devices, Cryotechnique: Poster Session
TT 10.5: Poster
Montag, 22. März 2010, 14:00–18:00, Poster A
Broadband magnetodielectric spectroscopy in the millikelvin-regime — •Christoph Grams, Tim Steinmetzer, Florian Waschkowski, Daniel Niermann, and Joachim Hemberger — 2. Physikalisches Institut, Universiät zu Köln, Deutschland
Broadband dielectric spectroscopy provides a wealth of information on the polarization dynamics in condensed matter. Our goal is to measure the complex permittivity from 1 Hz to 20 GHz inside a top loading dilution refrigerator at temperatures down to 20 mK and magnetic fields up to 13 T. We use a frequency response analyzer for frequencies up to 10 MHz with shielded coax cables for measurements of the complex impedance. From 10 MHz to 20 GHz we realize coaxial reflection measurements employing a network analyzer and a microstrip sample-holder. One of the major problems with this setup is the calibration due to the temperature dependent internal reflections. The broad frequency range of the network analyzer allows the use of time-domain-gating as a secondary error correction. We present our calibration results and first reference measurements, e.g. on SrTiO3 and the spin-ice Dy2Ti2O7.