Regensburg 2010 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 22: CE: Spin Systems and Itinerant Magnets
TT 22.14: Talk
Wednesday, March 24, 2010, 13:00–13:15, H21
High pressure studies in Ca3Ru2O7 — •Oliver Welzel1, Naoki Kikugawa2, Andrew Mackenzie3, and Malte Grosche1 — 1Cavendish Laboratory, University of Cambridge, UK — 2National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047, Japan — 3Scottish Universities Physics Alliance, School of Physics & Astronomy, University of St Andrews, UK
The bilayer ruthenate Ca3Ru2O7 undergoes first a magnetic transition (TN=56 K) and then a structural transition (TS = 48 K) on cooling. Most of the Fermi surface is gapped out at low temperature, leading to a very low carrier density and small Fermi surface pockets. Pressure suppresses both TN and TS and, for p>3.5 GPa, induces a third low temperature state, which has been known to be robust up to at least 7.5 GPa.
A detailed investigation of the unusual low temperature states of Ca3Ru2O7 across the pressure-temperature-field phase diagram requires reliable access to hydrostatic pressures up to and beyond 10 GPa. We apply lithographic patterning and sputtering processes to anvil pressure cells in order to produce complex but robust lead patterns, which are integrated into the anvil surface. Patterns include multi-turn coils as well as eight-lead configurations for resistivity measurements.
Resistivity data in Ca3Ru2O7 is presented, which indicates that the high pressure ordered state is fully suppressed at pc ≃ 9.5 GPa. Beyond pc, the in-plane resistivity follows a T5/3 power-law down to below 1 K, suggesting ferromagnetic quantum criticality