[{"type":"speech","title":"High-pressure magnetization measurements on single-crystalline CoS\u2082","issued":{"date-parts":[["2008"]]},"author":[{"family":"Drotziger","given":"S."},{"family":"Grube","given":"K."},{"family":"Uhlarz","given":"M."},{"family":"Pfleiderer","given":"C."},{"family":"Wilson","given":"J."},{"family":"L\u00f6hneysen","given":"H. von"}],"note":"72.Jahrestagung der Deutschen Physikalischen Gesellschaft und DPG Fr\u00fchjahrstagung des Arbeitskreises Festk\u00f6rperphysik, Fachverband Tiefe Temperaturen, Berlin, 25.-29.Februar 2008 Verhandlungen der Deutschen Physikalischen Gesellschaft, R.6, B.43(2008) TT 32.22","abstract":"Low Temperature Physics Division (TT)\nThursday\n[1] E. V. Sampathkumaran et al., Phys. Rev. B 47(13), 8349,\n(1993).\nTT 32.21\nThu 14:00\nPoster B\nUniaxial pressure and strain dependences of the characteristic energies in CeCu6\u2212x Aux \u2014 \u2022Kai Grube1 , Stefanie\n\u00a8\n\u00b4 \u00b4\n\u00a8\nsruhe, 76128 Karlsruhe, Germany \u2014 3 MPI f\u00a8 r chemische Physik fester\nSto\ufb00e, 01187 Dresden, Germany\nIf paramagnetic compounds are driven into a magnetically ordered\nstate by a nonthermal control parameter, the spontaneous symmetry\nbreaking in the ordered state, as well as the interplay of characteristic\nenergies inevitably lead to a change of the anisotropy of the compound\nat low temperatures. This can be used to identify the dominant energy scales and to study in more detail continuous phase transitions at\nzero temperature, i.e. so-called quantum critical points (QCP). The\narchetypical heavy-fermion system CeCu6\u2212x Aux is one of the best investigated examples of a magnetic QCP. It can easily be tuned across\nthe onset of antiferromagnetic order by changing its volume either by\nalloying with Au or applying pressure. For several distinct Au contents\nwe have determined the uniaxial pressure and strain dependences of the\nKondo and the magnetic interaction energies, with the Gr\u00a8 neisen pau\nrameter obtained through thermal expansion, speci\ufb01c heat, and compressibility measurements. The results show a strongly anisotropic\nantiferromagnetic phase which develops from a nearly isotropic Kondolattice state.\nTT 32.22\nThu 14:00\nPoster B\nHigh-pressure magnetization measurements on singlecrystalline CoS2 \u2014 \u2022Sandra Drotziger1 , Kai Grube2 , Marc\n\u00a8\nFestk\u00a8rperphysik, 76021 Karlsruhe \u2014 3 Physik Department E21, Techo\nLaboratory, University of Bristol, UK\nSuppression of magnetic order in weak itinerant magnets has recently\nattracted scienti\ufb01c interest due to novel phases emerging in the vicinity of a quantum phase transition. Among these systems, the pyrite\ncompound CoS2 is a promising candidate for general considerations\nas it has a simple cubic structure with high magnetic isotropy. At\nTC \u2248 122 K CoS2 develops ferromagnetic order with a spontaneous\nmoment of \u00b5s = 0.84 \u00b5B \/Co. With increasing pressure the ferromagnetism is suppressed to lower temperatures and the order of the phase\ntransition changes from second to \ufb01rst order at the tricritical point\np\u2217 \u2248 0.1 GPa [1]. For p > p\u2217 a \ufb01rst order \ufb01eld-induced phase transition is observed. We report pressure studies of the DC magnetization\nmeasurements on CoS2 single crystals as a function of temperature\ndown to 2.3 K and magnetic \ufb01eld up to 12 T. The measurements were\nperformed in a miniaturized diamond anvil cell made of a non-magnetic\nCuBe alloy. The temperature of the metamagnetic transition increases\nlinearly, with a slope almost independent of p.\n[1] S. Barakat, PhD Thesis, University of Cambridge (2001).\nTT 32.23\nThu 14:00\nPoster B\nCeRu2 Si2 and Quantum Critical Metamagnetism?\n\u2014\nG\u00a8ttingen \u2014 4 Institut f\u00a8r Theoretische Physik, Universit\u00a8t K\u00a8ln,\n50938 K\u00a8ln\nCeRu2 Si2 is a well-known prototypical heavy fermion system and\nshows a sudden strong increase in the magnetization M and the\nsample length \u2206L for magnetic \ufb01elds parallel to the crystallographic\nc-direction at around 7.8 T. These anomalies occur below 4 K and\nsharpen with decreasing temperatures, but no features for a \ufb01rst order\nphase transition are observed down to 15 mK.\nWe report new thermal expansion \u03b1, magnetostriction \u03bb and speci\ufb01c\nheat C\/T measurements, which have been made in mT magnetic \ufb01eld\nsteps around the metamagnetic crossover down to 15 mK on very pure\nsingle crystals.\nThe results show hints for the existence of a quantum critical endpoint in CeRu2 Si2 and were compared with an extended model of\nmetamagnetic quantum criticality, which was \ufb01rst introduced by Millis et al. in 2002.\nTT 32.24\nThu 14:00\nPoster B\nDevelopment of the magnetic order in Yb(Rh1\u2212x Cox )2 Si2 \u2014\n\u2022Christoph Klingner, Cornelius Krellner, Tanja Westerkamp,\nNiels Oeschler, Manuel Brando, Christoph Geibel, and Frank\nSteglich \u2014 Max Planck Institute for Chemical Physics of Solids, D01187 Dresden, Germany\nIn recent years YbRh2 Si2 has been intensively investigated due to its\nproximity to an antiferromagnetic quantum critical point (QCP). As\nexpected for Yb-Kondo lattice compounds the magnetic ordering of\nYbRh2 Si2 (TN =70mK) can be shifted to higher temperature by applying pressure. Doping with Cobalt results in positive chemical pressure, allowing therefore the investigation of the magnetic phase diagram and the behavior while stabilizing the antiferromagnetic ordered\nstate. The advantage of less complex measurements compared to high\npressure experiments leads to more detailed and precise results than\nin pressure studies. In this contribution we report on the growth of a\nseries of single crystals Yb(Rh1\u2212x Cox )2 Si2 with concentrations x between 0 and 1. The low temperature properties studied by resistivity,\nspeci\ufb01c heat and magnetization measurements for di\ufb00erent concentrations will be presented. Further on the behaviour of the transitions\nunder an applied magnetic \ufb01eld will be discussed. Finally, a phase\ndiagram of Yb(Rh1\u2212x Cox )2 Si2 will be presented and compared with\nthe pressure phase diagram of YbRh2 Si2 .\nTT 32.25\nThu 14:00\nPoster B\nThermodynamics of Spin-Ladder and Spin-Chain Systems\nclose to Quantum Criticality \u2014 \u2022J. Rohrkamp1 , T. Lorenz1 , A.\n\u00a8\nK. Kramer3 , and M. M. Turnbull4 \u2014 1 II. Physikalisches Institut,\nzu K\u00a8ln \u2014 3 Department of Chemistry and Biochemistry, University\nof Bern \u2014 4 Carlson School of Chemistry and Department of Physics,\nClark University\nCompounds with magnetic subsystems representing simple model spin\nsystems with weak magnetic coupling constants are ideal candidates to\ntest theoretical predictions for the generic behavior close to quantum\nphase transitions. We present measurements of the thermal expansion,\nmagnetostriction and thermal conductivity of the spin- 1 -ladder system\n2\n1\npiperidinium copper bromide (C5 H12 N)2 CuBr4 and the spin- 2 -chain\ncompound copper pyrazine dinitrate Cu(C4 H4 N2 )(NO3 )2 . Both compounds show quantum phase transitions as a function of magnetic \ufb01eld\nwith pressure dependent\u221a\ncritical \ufb01elds. The low-temperature thermal\nexpansion approaches 1\/ T divergences at the critical \ufb01elds and shows\na complex behavior with various sign changes inbetween.\nTT 32.26\nThu 14:00\nPoster B\nSearch for coupled S=1\/2 dimer systems in a new class\n\u00b4\nof nitronyl nitroxides biradicals \u2014 \u2022K. Removic-Langer11 , U.\nWolf1 , and M. Lang1 \u2014 1 Physikalisches Institut, J.W. GoetheUniversit\u00a8t, Max-von-Laue-Str. 1, SFB\/TR 49, D-60438 Franka\nRecently, quantum magnets such as coupled-dimer systems and easyplane antiferromagnets have emerged as interesting objects for studying the properties of magnetic \ufb01eld-induced Bose-Einstein condensation (BEC). Up until the present day, most of the studies have been","kit-publication-id":"220071131"}]