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SYEC: Materials under extreme conditions
SYEC 2: Extreme Conditions II
SYEC 2.3: Hauptvortrag
Mittwoch, 26. März 2003, 17:00–17:30, HSZ/01
AC-calorimetry at very high pressure and low temperature — •Heribert Wilhelm1 and Didier Jaccard2 — 1Max Planck Institut für Chemische Physik fester Stoffe, Nöthnitzer-Str. 40, D-01187 Dresden — 2DPMC, University of Geneva, Quai E.-Ansermet 24, CH-1211 Geneva 4
The pressure-temperature (p,T) phase diagram of strongly correlated electron systems at low temperature is commonly explored by electrical resistivity measurements for pressures up to 25 GPa, using an anvil-type of high pressure cell. It is, however, desirable to measure thermodynamic quantities, notably the specific heat in these extreme conditions. The accessible pressure range for specific heat experiments was limited to 2-3 GPa since adiabatic techniques demand large sample masses and thus, a large cell volume. For higher pressures a much smaller sample volume is required. Among the non-adiabatic methods, the ac-calorimetry is a suitable technique to be adopted to the conditions in an anvil-type of high pressure cell. A combined measurement of electrical resistivity ρ(T) and ac-calorimetry of the magnetically ordered CePd2.02Ge1.98 in the temperature range 0.3 K < T < 10 K for pressures up to 22 GPa will be reported. The pressure dependence of the Néel temperature could be deduced from the anomaly observed in the ac-signal and in ρ(T). The inverse of the ac-signal 1/Vac ∝ C/T recorded at the lowest temperature is strongly pressure dependent and shows a pronounced peak in the vicinity of the magnetic/non-magnetic borderline.