[{"type":"speech","title":"Hall effect near the quantum critical point of CeCu\u2086\u208b\u2093Au\u2093","issued":{"date-parts":[["2006"]]},"author":[{"family":"R\u00f6ger","given":"M."},{"family":"Uhlarz","given":"M."},{"family":"Putselyk","given":"S."},{"family":"Stockert","given":"O."},{"family":"L\u00f6hneysen","given":"H. von"}],"note":"DPG Spring Meeting of the Divison Condensed Matter, 21st General Conf.of the Condensed Matter Division of the European Physical Society, Dresden, March 26-31, 2006 Verhandlungen der Deutschen Physikalischen Gesellschaft, R.6, B.41(2006) TT 25.59","abstract":"Low Temperature Physics\nnetic reference compound LuRh2 Si2 in the temperature range between\n30 mK and room temperature are presented and discussed within the\nframework of current theoretical models.\nThe high temperature transport properties are dominated by the transition from incoherent to coherent Kondo scattering and furthermore by\nthe crystal electric \ufb01eld splitting of the Yb3+ ions, as the \ufb01rst excited\ndoublet is situated at 200 K. The low temperature regime is governed by\nthe strong NFL behavior due to the proximity of the antiferromagnetic\ninstability.\nTT 25.57 Wed 14:30 P1\nSingle crystal growth and investigation of the magnetism of the\nalloy CePd1\u2212x Rhx for concentrations x \u2265 0.6 \u2014 \u2022M. Deppe1 , P.\nPedrazzini2 , N. Caroca-Canales1 , C. Geibel1 , and J.G. Sereni3\n\u2014 1 Max-Planck-Institute for Chemical Physics of Solids, N\u00a8thnitzer Str.\n40, 01187 Dresden, Germany \u2014 2 DPMC-Universit\u00b4 de Gen`ve, Q. Ernest\n- Ansermet, 1211 Gen`ve, Switzerland \u2014 3 Lab. Bajas Temperaturas,\nCentro At\u00b4mico Bariloche (CNEA), 8400 S.C. de Bariloche, Argentina\nIn the orthorhombic alloy CePd1\u2212x Rhx the continuous decrease of the\nferromagnetic ground state T C (x) can be followed over more than a\ndecade in T , from 6.6 K for x = 0 to 0.25 K at x = 0.8. Additional low\ntemperature measurements suggest a smeared ferromagnetic quantumcritical point (QCP) for xcr between 0.87 and 0.9.\nAll these results were based on CePd1\u2212x Rhx polycrystals. In order to\nget a more precise insight into the magnetic behaviour in the critical\nregion we grow CePd1\u2212x Rhx single crystals in the range x \u2265 0.6. We\nused the Bridgman technique with a pulling rate of 3-5 mm. Di\ufb00erential\nthermoanalysis measurements indicate a low melting point Tm = 1090 \u00b1\n15 \u25e6 C. The lattice parameters were de\ufb01ned with X-ray powder di\ufb00raction and the composition was investigated with microprobe analysis. We\nperformed speci\ufb01c heat and resistivity measurements down to 0.4 K and\ncompare our results with the previous results on polycrystalline samples.\nFurther we studied the decrease of the magnetic anisotropy with x by\nsusceptibility and magnetization measurements. These results will be\ndiscussed in relation to the scenario for the critical concentration.\nTT 25.58 Wed 14:30 P1\nUltra-low-temperature speci\ufb01c heat of CePd1\u2212x Rhx \u2013 smeared\nferromagnetic quantum phase transition \u2014 \u2022Adam Pikul, Tanja\nPhilipp Gegenwart, Julian Sereni, and Christoph Geibel \u2014\nThe CePd1\u2212x Rhx system exhibits a continuous evolution from ferromagnetic (FM) order in CePd (TC = 6.5 K) to an intermediate\u2013valence\nground state in CeRh [1]. In the present contribution we report on results\nof low-temperature speci\ufb01c-heat measurements performed for polycrystalline samples of CePd1\u2212x Rhx , with the compositions 0.8 \u2264 x \u2264 0.95,\nwhich are supposed to be close to a FM quantum critical point [1].\nIn contrast to CePd0.2 Rh0.8 , still demonstrating the FM phase transition at TC = 370 mK, the C(T ) curve measured for CePd0.15 Rh0.85\ndoes not show any anomaly at least down to 70 mK. In the latter compound C\/T \u223c \u2212 ln T , characteristic of a non-Fermi-liquid (NFL) system,\nand achieves a value of almost 1 J\/(mol K2 ) at 70 mK. Upon further\nincreasing of the Rh-content the value of C\/T decreases, but the NFL\nbehavior is still well visible in the samples with 0.87 \u2264 x \u2264 0.95, for\nwhich C\/T \u223c T \u2212\u03b1 (\u03b1 \u2248 0.5). Upon applying magnetic \ufb01elds FL behavior C\/T (T ) \u223c const. is recovered in all di\ufb00erent samples.\nThe above-mentioned results indicate that the NFL behavior is observed down to mK-temperatures over an extended x-range (0.85 \u00f7 0.95).\nThis would be compatible with a smeared quantum phase transition.\nA. Pikul\u2019s attendance at this conference was sponsored by the Humboldt Foundation.\n[1] J. G. Sereni, R. K\u00a8chler, C. Geibel, Physica B 359\u2013361 (2005) 41\nTT 25.59 Wed 14:30 P1\nHall e\ufb00ect near the quantum critical point of CeCu6\u2212x Aux \u2014\n\u00a8\n\u2022M. Roger1 , M. Uhlarz1 , S. Putselyk1 , O. Stockert2 , and H. v.\n\u00a8\nFestk\u00a8rperphysik, D-76021 Karlsruhe\nThe heavy-fermion system CeCu6\u2212x Aux orders antiferromagnetically\nabove xc = 0.1. The quantum phase transition at xc displays unusual features, e.g., low-dimensional spin \ufb02uctuations and locally critical slowing down of these spin \ufb02uctuations suggestive of a breakdown\nof the Kondo coupling between 4f and conduction electrons [1]. This\nWednesday\nbreakdown should be re\ufb02ected in the Hall e\ufb00ect [2]. The Hall e\ufb00ect of\nCeCu6\u2212x Aux (0 \u2264 x \u2264 0.2) as measured in a \ufb01nite \ufb01eld (B = 0.3 T)\nalong the magnetically easy c axis has shown Fermi-liquid behavior at\nlow T , i.e. a temperature-independent Hall constant RH below \u223c 0.3 K\n[3]. Applying the magnetic \ufb01eld parallel to the magnetically hard b-axis\n(anisotropy factor \u223c 10) allows to detect the e\ufb00ect of magnetic order on\nRH for x = 0.2 and of quantum criticality for x = 0.1.\n[1] A. Schr\u00a8der et al., Nature 407, 6802 (2000)\n[2] P. Coleman et al., J. Phys. Cond. Matt. 13, R723 (2001)\n[3] H. Bartolf et al., Physica B 359-363, 86 (2005)\nTT 25.60 Wed 14:30 P1\nExperimental Study of the Hall E\ufb00ect and Magnetoresistance\n\u00a8\nNiklowitz, and Peter Boni \u2014 Physik Department E21, Technische Universit\u00a8t M\u00a8nchen, James-Franck-Strasse, D-85748 Garching, Gera\nmany\nThe itinerant-electron magnet MnSi orders magnetically at Tc =\n29.5 K. The magnetic state is characterised by a helical modulation along\nthe 111 space diagonal in the cubic B20 structure. Magnetic \ufb01eld suppresses the helical order above 0.6 T. The properties of MnSi are in various ways remarkable. The temperature dependence of the electrical resistivity suggests the emergences of an extended non-Fermi liquid phase\nabove pc = 14.6 kbar. Neutron scattering at ambient pressure shows an\nanomalous \ufb01eld dependence of helical \ufb02uctuations which may indicate\ncertain similarities with the presence of partial magnetic order akin liquid crystals observed in a pocket of the NFL-phase. Here we report a\ndetailed study of the Hall e\ufb00ect and the magnetoresistance of MnSi. We\nfocus in particular on normal and anomalous contributions to the Hall\ne\ufb00ect and consider similarities and di\ufb00erences with conventional ferromagnets.\nTT 25.61 Wed 14:30 P1\nMagnetocaloric e\ufb00ect and Gr\u00a8 neisen parameter of thespin-gap\nsystem TlCuCl3 \u2014 \u2022S. Stark1 , N. Johannsen1 , T. Zabel1 ,\nO. Heyer1 , A. Oosawa2 , H. Tanaka3 , A. Vasiliev4 , and T.\n\u2014 2 Advanced Science Research Center,Japan Atomic Energy Research\nInstitute, Japan \u2014 3 Dep. ofPhysics, Tokyo Institute of Technology,\nJapan \u2014 4 LowTemp. Physics Dep., Moscow State University, Russia\nTlCuCl3 is a S = 1 quantum system with a nonmagnetic singlet ground\n2\nstate and a small energy gap to the excited triplet states. A magnetic \ufb01eld\nH > 6 T induces 3D antiferromagnetic order with a staggered magnetization perpendicular to the applied \ufb01eld. This transition can be described\nby a Bose-Einstein condensation of magnons and represents an example\nfor a \ufb01eld-induced quantum phase transition. We present a study of the\nmagnetocaloric e\ufb00ect, the thermal expansion \u03b1, the speci\ufb01c heat cp and\nthe magnetostriction. There exist clear predictions for the behavior of\nthese quantities near a quantum critical point [1]. The di\ufb00erential magdT\nnetocaloric e\ufb00ect \u03b8 = dB and the Gr\u00a8neisen parameter \u0393 = c\u03b1 are very\nconvenient to determine a possible quantum critical behavior of TlCuCl3 ,\n1\n\u03b8\nsince one anticipates that both \u0393 and T diverge (\u223c T ) for T \u2192 0 and\nB \u2192 Bc . Using Ehrenfest relations we also derive the uniaxial pressure\ndependence of the phase boundary [2]. We performed our mea","kit-publication-id":"230063979"}]