Bulletin of the American Physical Society
2007 APS March Meeting
Volume 52, Number 1
Monday–Friday, March 5–9, 2007; Denver, Colorado
Session P10: URu2Si2 and Related Compounds |
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Sponsoring Units: DCMP Chair: Filip Ronning, Los Alamos National Laboratory Room: Colorado Convention Center Korbel 1E |
Wednesday, March 7, 2007 11:15AM - 11:27AM |
P10.00001: Effects of Rhenium doping on the high magnetic field versus temperature phase diagram of URu2Si2 Sonia Francoual, Neil Harrison, Marcello Jaime, Scott Baily, Alex Lacerda, Nicholas Butch, Brian Maple Magnetoresistance and magnetization measurements carried out in URu$_{2-x}$Re$_{x}$Si$_{2}$ at low temperatures and high magnetic fields for x values of the rhenium doping between 0.01 and 0.10 enable us to investigate the robustness of the multiple ordered phases previously identified in URu$_{2}$Si$_{2}$ near the putative metamagnetic quantum critical point at fields around 37 $\pm $ 1 T. From the transport study, rhenium doping is shown to reduce considerably the elliptical region occupied by the hidden order phase in the (H, T) phase diagram and to shift to lower fields the broad magnetoresistivity maximum observed in the high temperature phase. In addition, the upper temperature limit at which the field-induced phase transitions are observed inside the metamagnetic crossover region in the magnetization curves decreases rapidly with increasing rhenium doping. All results tend to indicate that for x $<$ 0.10 the dilute substitution of Re in place of Ru in URu$_{2}$Si$_{2}$, unlike Rh substitution, weaken the ordering in the vicinity of the putative quantum critical point. [Preview Abstract] |
Wednesday, March 7, 2007 11:27AM - 11:39AM |
P10.00002: Field-induced Fermi surface reconstruction and adiabatic continuity between antiferromagnetism and hidden-order state in URu$_2$Si$_2$ Y.J. Jo, L. Balicas, C. Capan, K. Behnia, P. Lejay, J. Flouquet, J.A. Mydosh, P. Schlottmann Shubnikov-de Haas oscillations at very low temperatures and high magnetic fields reveal an abrupt reconstruction of the Fermi surface within the hidden-order phase of URu$_{2}$Si$_{2}$. Taken together with reported Hall effect results, this implies an increase in the effective carrier density and suggests spectrum of itinerant quasiparticles. While hydrostatic pressure favors antiferromagnetism in detriment to the hidden-order state, we found that it has a modest effect on the complex $H-T$ phase diagram. This suggests adiabatic continuity between the hidden-order and antiferromagnetism. [Preview Abstract] |
Wednesday, March 7, 2007 11:39AM - 11:51AM |
P10.00003: Interplay between Fermi surface topology and ordering in URu$_{2}$Si$_{2}$ revealed through abrupt Hall coefficient changes Yoon Seok Oh, Kee Hoon Kim, P. A. Sharma, N. Harrison, H. Amitsuka, J. A. Mydosh The Hall effect is becoming recognized as a viable alternative for understanding Fermi surface(FS) changes in $f$-electron antiferromagnets and ferromagnets tuned close to quantum criticality. Any knowledge of the extent to which the $f$- electrons contribute to the FS topology is of crucial importance for understanding the nature of the ordering and the fate of the heavy quasiparticles. We show that Hall effect measurements extended to high magnetic fields uncover an intricate level of interplay between the FS topology and the stability of the various phases of pure and 4~\% Rh-doped URu$_2$Si$_2$. At low $H$ and $T$, the enhancement of the Hall coefficient and Hall angle shows that the otherwise large FS is reconstructed into small high mobility pockets below $T_{\rm o}$ in URu$_2$Si$_2$: a finding that is ubiquitous among imperfectly-nested itinerant forms of broken translational symmetry groundstates. This groundstate is then destabilized when a magnetic field causes two of the high mobility pockets to become spin polarized, ultimately leading to its destruction at $\approx$~35~T. Intermediate larger and strongly polarized FSs appear in phases II, III and V before a fully polarized unreconstructed FS is achieved beyond $\approx$~39~T with 1 hole/U and 1.5~$\mu_{\rm B}$/U. [Preview Abstract] |
Wednesday, March 7, 2007 11:51AM - 12:03PM |
P10.00004: NMR Study of Line Shape Effects Caused by the Hidden Order in a Random Powder of URu$_2$Si$_2$ S. Jung, O. O. Bernal, D. E. MacLaughlin, T. J. Gortenmulder, J. A. Mydosh We present NMR data for an epoxy-potted random-powder sample of URu$_2$Si$_2$. We have followed the line shape from 280 K down to about 4 K and observed its changing features as functions of temperature and two values of the applied magnetic field strength (1 and 2 T). We will describe the effects of the hidden order (transition temperature $T_0 \sim 17.5$~K) on the line shape and compare them with previous results in c-axis oriented samples and single crystals. [Preview Abstract] |
Wednesday, March 7, 2007 12:03PM - 12:15PM |
P10.00005: Inelastic neutron scattering studies of itinerant spin excitations in URu2Si2 near the hidden order transition John Janik, G. MacDougall, G. Luke, Y.-J. Jo, L. Balicas, Y. Qiu, J. Copley, Z. Yamani, B. Buyers, C. Wiebe We performed extensive neutron scattering studies on the heavy fermion superconductor URu$_{2}$Si$_{2}$. Using the C5 triple axis spectrometer at Chalk River, we studied the spin excitations recently reported [C. R. Wiebe, J. A. Janik et al, Nature Physics] above and below the T$_{0}$ transition. It has become clear from our previous work that these incommensurate itinerant spin excitations account for the entropy change into the hidden order (HO) state. This severely limits the possible theoretical scenarios on the ground state of the HO phase. [Preview Abstract] |
Wednesday, March 7, 2007 12:15PM - 12:27PM |
P10.00006: The Evolution of the Hidden Order Phase in URu$_{2-x}$Re$_x$Si$_2$ under Pressure J.R. Jeffries, N.P. Butch, B.T. Yukich, M.B. Maple The heavy fermion compound URu$_2$Si$_2$ exhibits three distinct ordered states as a function of temperature and pressure: ``hidden order'' (HO), in which the order parameter has yet to be identified; antiferromagnetism (AFM), which seemingly develops out of the HO state at $P \leq 15$ kbar; and superconductivity (SC), which exists at ambient pressure. While URu$_2$Si$_2$,the parent compound of the URu$_{2-x}$Re$_x$Si$_2$ system, has been the subject of much scrutiny in the past several years, the nature of the HO phase is still uncertain. The evolution of the ordered phases as a function of pressure in the URu$_{2-x}$Re$_x$Si$_2$ system could provide clues to or constraints on the elusive order parameter of this HO phase. To this end, oriented single crystal samples of URu$_{2-x}$Re$_x$Si$_2$ with small values of $x$ have been synthesized and investigated under nearly hydrostatic pressure via electrical resistivity measurements. While the SC in URu$_{2-x}$Re$_x$Si$_2$ is rapidly suppressed with Re concentration, the HO phase persists up to $x~\approx~0.1$. The pressure dependence of the HO phase in this concentration range will be discussed along with possible consequences to the ordered states. This research was sponsored by the U.S. DOE under Research Grant No. DE-FG02-04ER46105 and by the U.S. NNSA under the Stewardship Science Academic Alliances program through DOE Research Grant No. DE-FG52-03NA00068. [Preview Abstract] |
Wednesday, March 7, 2007 12:27PM - 12:39PM |
P10.00007: The Search for Quantum Criticality in the URu$_{2-x}$Re$_{x}$Si$_{2}$ Phase Diagram N.P. Butch, J.R. Jeffries, B.T. Yukich, T.A. Sayles, J. Paglione, P.-C. Ho, M.B. Maple It has been established that as Re is doped into polycrystalline URu$_{2}$Si$_{2}$, the hidden order/antiferromagnetic and superconducting phases are suppressed, while at intermediate doping, long range ferromagnetism emerges. To further investigate observations of the persistence of non-Fermi liquid behavior well into the ferromagnetic phase, we have prepared single crystals of URu$_{2-x}$Re$_{x}$Si$_{2}$ in the Re concentration range of $0 \leq x \leq 0.6$ and performed magnetization, electrical and thermal transport, and calorimetry measurements at low temperatures down to $0.1$~K. [Preview Abstract] |
Wednesday, March 7, 2007 12:39PM - 12:51PM |
P10.00008: Crystal fields, magnetoresistance, and superconductivity of Pr$_{1-x}$La$_{x}$Os$_{4}$Sb$_{12}$ Bohdan Andraka, Costel R. Rotundu, Martin E. McBriarty Investigation of Pr$_{1-x}$La$_{x}$Os$_{4}$Sb$_{12}$ in strong magnetic fields implies that crystalline electric field (CEF) energies of Pr are unchanged to at least x=0.2. CEF energies for x=0.4 are approximately 20 {\%} larger than for x=0.2 and increase further for x=0.67. Specific heat discontinuity at T$_{c}$ and the upeer critical field slope at T$_{c}$ indicate that the strongest suppression of m* takes place between x=0 and x$_{cr}\sim $0.3. High accuracy specific heat data obtained on a large crystal of x=0.67 exhibit significant deviations with respect to the Schottky specific heat corresponding to singlet-triplet excitations. Similar deviations are seen for other crystals with x$>$x$_{cr}$. On the other hand, magnetoresistance of moderately and strongly dilute alloys is consistent with predictions for a singlet-triplet CEF model. Correlations between these measurements of CEF's and superconductivity of Pr$_{1-x}$La$_{x}$Os$_{4}$Sb$_{12}$ will be discussed. Also, evidences against and for homogeneous coexistence of two superconducting transitions in the specific heat of pure PrOs$_{4}$Sb$_{12}$ will be presented and discussed. [Preview Abstract] |
Wednesday, March 7, 2007 12:51PM - 1:03PM |
P10.00009: A comparison of the normal and superconducting state properties of Pr(Os$_{1-x}$Ru$_x$)$_4$Sb$_{12}$ and Pr$_{1-x}$Nd$_x$Os$_4$Sb$_{12}$ P.-C. Ho, T. Yanagisawa, N.P. Butch, W.M. Yuhasz, N.A. Frederick, M.B. Maple The evolution of unconventional superconductivity and the high field ordered phase (HFOP), the latter of which has been identified with antiferroquadrupolar order, in PrOs$_4$Sb$_{12}$ has been investigated in two pseudoternary systems, Pr(Os$_{1-x}$Ru$_x$)$_4$Sb$_{12}$ and Pr$_{1-x}$Nd$_x$Os$_4$Sb$_{12}$. In the Pr(Os$_{1-x}$Ru$_x$)$_4$Sb$_{12}$ system, the superconducting transition temperature $T_{c}$ is suppressed nearly linearly with $x$ to a minimum at $x = 0.6$ from both end member compounds, the upper critical field $H_{c2}$ has an approximately linear dependence on $T$ for $x > 0.4$, and the features related to the HFOP in the electrical resistivity disappear for $x \ge 0.1 $. On the other hand, in the Pr$_{1-x} $Nd$_x$Os$_4$Sb$_{12}$ system, $T_{c}$ and the Curie temperature $\Theta_{C}$ are suppressed monotonically toward $x = 0.55$ from $x=0$ and $x=1$, respectively, no linear $T$ dependence of $H_{c2}$ is observed, the HFOP persists up to at least $x \sim 0.45$, and there is an indication of the coexistence of superconductivity and ferromagnetism for $x \sim 0.45$ according to specific heat measurements. In both systems, $H_{c2}(T)$ is limited by the orbital motion of the electrons and the decrease of $T_{c}$ with $x$ from $x=0$ is nearly the same. [Preview Abstract] |
Wednesday, March 7, 2007 1:03PM - 1:15PM |
P10.00010: The disordered ground state of quantum critical Ce(Ru$_{1-x}$Fe$_x$)$_2$Ge$_2$ Wouter Montfrooij, Jagat Lamsal, Meigan Aronson, Marcus Bennett, Anne de Visser, Huang Ying Kai, Nguyen Thanh Huy, Mark Lumsden, Mohana Yethiraj, Yiming Qiu We present neutron scattering data that show that magnetic ordering in the vicinity of a quantum critical point is restricted to short length scales. Remarkably, the spatial extent of the magnetic correlations is independent of the inter- moment distances. We argue that our data on Ce(Ru$_{1-x}$Fe$_x$)$_2$Ge$_2$ demonstrate that quantum fluctuations disorder the system and dilute the magnetic moments to such an extent that the response of the system is disorder dominated. Our observations naturally explain how E/T- scaling is possible in systems whose apparent dimensionality is above the upper critical dimension. [Preview Abstract] |
Wednesday, March 7, 2007 1:15PM - 1:27PM |
P10.00011: Magnetic field tuning of the low temperature state in YbNiSi$_3$: magnetic field induced quantum criticality Marcos A. Avila, Toshiro Takabatake, Sergey L. Bud'ko, Paul C. Canfield We present detailed, low temperature, magnetoresistance and specific heat data from measurements on YbNiSi$_3$ in magnetic field applied along the easy magnetic axis, $H \| b$. Initially the antiferromagnetic ground state changes into a field-induced metamagnetic phase at $\sim 16$ kOe ($T \to 0$). On further increase of magnetic field, magnetic order is suppressed to below 0.4 K at $\sim 85$ kOe. The functional behavior of the resistivity and specific heat is discussed in comparison with that of the few other stoichiometric, heavy fermion compounds with established field-induced quantum criticality. [Preview Abstract] |
Wednesday, March 7, 2007 1:27PM - 1:39PM |
P10.00012: Thermal Transport in ZrZn$_2$ - Probing the Marginal Fermi Liquid State Michael Sutherland, R. Smith, K. Noriaki, G.G. Lonzarich, S. Takashima, M. Nohara, H. Takagi The electronic properties of metals on the border of magnetism are often found to exhibit unusual temperature dependencies, not easily understood within a conventional Fermi liquid picture. The weak itinerant ferromagnet ZrZn$_2$ is a notable example, where resistivity evolves at low temperatures as T$^{5/3}$ as a result of spin fluctuation scattering. Here we investigate the effects of these fluctuations on heat transport, by measuring thermal conductivity to low temperatures in high quality samples. We compare these results to expectations from spin fluctuation theory, and comment on the relative effectiveness of spin fluctuations at degrading heat and charge currents. [Preview Abstract] |
Wednesday, March 7, 2007 1:39PM - 1:51PM |
P10.00013: ABSTRACT HAS BEEN MOVED TO R1 |
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