Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session Q22: Heavy Fermions: Ce-based Compounds: Experiment |
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Sponsoring Units: DCMP Chair: Sergey Bud'ko, Ames Laboratory/Iowa State University Room: 202A |
Wednesday, March 4, 2015 2:30PM - 2:42PM |
Q22.00001: Surface bulk differences in a Kondo lattice system Kalobaran Maiti, Thomas Pruschke, Khadiza Ali, Deepnarayan Biswas, Sangeeta Thakur, Swapnil Patil, Nishaina Sahadev, Ganesh Adhikary, G. Balakrishnan Antiparallel coupling between the magnetic moment and conduction electrons leads to a non-magnetic Fermi liquid phase in a magnetic material - this is known as Kondo effect. Such coupled electronic states appear as a sharp feature at the chemical potential at low temperatures, called Kondo resonance feature. Photoemission spectra of Kondo systems often exhibit growth of multiple Kondo resonance features with large intensity at temperatures much higher than the Kondo temperature. We studied the evolution of the Kondo resonance feature in CeB6 employing high resolution photoemission spectroscopy and state of the art calculations based on dynamical mean field theory. We observe multiple Kondo resonance features with anomalies in their temperature evolution. It appears that the surface of these systems possess high Kondo temperature compared the bulk that causes unusual temperature evolution in these materials. [Preview Abstract] |
Wednesday, March 4, 2015 2:42PM - 2:54PM |
Q22.00002: Spin fluctuations in the Kondo Semimetal CeRu4Sn6 Wesley Fuhrman, J. Haenel, A. Prokofiev, S. Paschen, D.T. Adroja, J.A. Rodriguez, C.L. Broholm We present neutron scattering results for CeRu4Sn6. Tentatively classified as one of the few non-cubic Kondo insulators, CeRu4Sn6 has highly anisotropic physical properties. Using cold neutron inelastic neutron scattering, we have identified a magnetic signal for $\hbar\omega < 1$ meV with a 4$f$ like form factor and Q-dependence that is indicative of anisotropic antiferromagnetic spin correlations.The implications for the classification and understanding of CeRu4Sn6 are discussed. [Preview Abstract] |
Wednesday, March 4, 2015 2:54PM - 3:06PM |
Q22.00003: Quantum Criticality in Kondo Compound CeAgBi2 Sean Thomas, Priscila Rosa, Zachary Fisk, Jing Xia We report a systematic study of the dense Kondo compound CeAgBi$_{2}$ by means of electrical resistivity, heat capacity, and magnetic measurements, including torque magnetometry and Sagnac interferometry. By comparing our results with previous reports, we observe at zero field a slightly larger antiferromagnetic ordering temperature at $T_{N} = 6.4$ K. Moreover, five field-induced metamagnetic transitions are observed in magnetic fields up to $12$ T applied parallel to the $c$-axis, including a remarkable signature for a first order transition at $H_{c}\sim 8$ T. The low temperature specific heat coefficient $\gamma$ and the $T^{2}$ resistivity coefficient also show a divergence at the same $H$, indicating a putative quantum critical point. This work is supported by NSF grant DMR-1350122. The development of Sagnac interferometer is supported by NSF grant ECCS-1346603. [Preview Abstract] |
Wednesday, March 4, 2015 3:06PM - 3:18PM |
Q22.00004: Doping Dependence of the Structural and Magnetic Properties of CeCu$_{6-x}$T$_{x}$ (T = Ag, Pd) L. Poudel, M.A. McGuire, C. de la Cruz, S. Calder, A.F. May, W. Tian, M. Matsuda, H.B. Cao, T. Hong, A.E. Payzant, H. Jeen, H.N. Lee, M. Koehler, H. Zhou, V. Keppens, D. Mandrus, A.D. Christianson CeCu$_{6-x}$Au$_x$ is a well-known heavy fermion system that exhibits an antiferromagnetic quantum critical point(QCP) at x $\sim$ 0.1. The end-member, CeCu$_6$ undergoes a structural transition, which is suppressed as Cu is partially substituted by Au in CeCu$_{6-x}$Au$_x$: the critical concentration being at x$\sim$0.1. This critical point occurs in close proximity to the antiferromagnetic QCP. Here, we study related systems, CeCu$_{6-x}$Ag$_x$ and CeCu$_{6-x}$Pd$_x$, to determine more globally the role of structural degrees of freedom in the observed critical behavior. For magnetically ordered compositions of CeCu$_{6-x}$Ag$_x$ and CeCu$_{6-x}$Pd$_x$, we find a long-range order with the wave-vector similar to that observed in CeCu$_{6-x}$Au$_x$. The structural transition temperature of CeCu$_{6-x}$Ag$_x$ decreases linearly with Ag concentration until the transition is completely suppressed at x$\sim$0.1. In contrast, moderate Pd-doping does not affect the structural transition, which is observed in CeCu$_{6-x}$Pd$_x$ with x $\leq$ 0.4. [Preview Abstract] |
Wednesday, March 4, 2015 3:18PM - 3:30PM |
Q22.00005: High Magnetic Field Properties of Ce$_{2}$Rh$_{3}$Ge$_{5}$ Mark Wartenbe The competition between localized and delocalized f electrons in heavy fermion materials produces a wide variety of interesting physical phenomena. Among these compounds is Ce2Rh3Ge5. This heavy-fermion system undergoes an antiferromagnetic transition below 4K and exhibits an angle dependent magnetic phase transition around 25 tesla. In addition, RF conductivity measurements in pulsed field (65T) have revealed quantum oscillations. Temperature dependence at fixed angle indicates relatively heavy effective masses of values ranging from around 3m$_{\mathrm{e}}$ on up to 10m$_{\mathrm{e}}$. This indicates that the narrow f-electron density of states is partially hybridized close to the Fermi energy, but also places strict cryogenic constraints upon the measurement ($^{3}$Helium temperatures are required). Fermi surface calculations have produced complex figures which lend validation to such rich behavior. [Preview Abstract] |
Wednesday, March 4, 2015 3:30PM - 3:42PM |
Q22.00006: $^{119}$Sn NMR studies on the heavy fermion compound CeSn$_{3}$ John Crocker, Andrew Kim, Peter Klavins, Nicholas Curro CeSn$_{3}$ does not exhibit long-range order at low temperatures, thus it provides an interesting baseline for NMR studies of the Knight shift. We report the synthesis and characterization of single crystals of CeSn$_{3}$, as well as $^{119}$Sn nuclear magnetic resonance (NMR) measurements from 4.5K to room temperature. Our data reveal a broad peak in the knight shift (K) at T$_{\mathrm{max}}\approx $ 135K, and a knight shift anomaly at T* $\approx $ 85K. [Preview Abstract] |
Wednesday, March 4, 2015 3:42PM - 3:54PM |
Q22.00007: Magnetic structure and CEF levels in CeNiAsO S. Wu, C. Broholm, W.A. Phelan, T.M. McQueen, J.C. Neuefeind, M.B. Stone Some HF materials like CeCu6-xAux and YbRh2Si2 have been interpreted as exhibiting unconventional local criticality, rather than a conventional magnetic instability. However, the situation is far from settled so there is great interest in exploring new HF systems in the proximity of magnetic instabilities. Recent reports on CeNiAsO indicate this is a good candidate for such studies. CeNiAsO is isotructural to the 1111 Fe-based superconductors but exhibits a different type of itinerant magnetism associate with the rare earth site. CeNiAsO has two successive phase transitions at 9.3K and 7.3K that were tentatively associated with antiferromagnetism. To understand these transitions, we carried out magnetic neutron diffraction experiments at the Spallation Neutron Source. We have identified the long range magnetic order and associate the lower transition with a reorientation of the magnetic moment. We also report inelastic neutron powder experiments that determine the crystal field level scheme, which differs from that reported for CeFeAsO and corroborate our analysis of the magnetic structure. [Preview Abstract] |
Wednesday, March 4, 2015 3:54PM - 4:06PM |
Q22.00008: Momentum space structure of quasielastic spin fluctuations in Ce$_{3}$Pd$_{20}$Si$_{6}$ Alistair Cameron, Pavlo Portnichenko, Maksym Surmach, Pascale Deen, Silke Paschen, Andrey Prokofiev, Jean-Michel Mignot, Andr\'e Strydom, Mark Telling, Andrey Podlesnyak, Dmytro Inosov Ce$_{3}$Pd$_{20}$Si$_{6}$ is one of the heaviest electron systems amongst the heavy-Fermion metals. We have used high-resolution neutron spectroscopy to observe the low-energy region of magnetic scattering from the paramagnetic state, finding that at low temperatures the quasielastic magnetic response is present throughout the Brillouin zone. It forms a broad hump, centred at the (111) scattering vector, surrounded by minima of intensity at (002), (220) and the equivalent wavevectors. This momentum space structure distinguishes it from a simple crystal-field excitation, as proposed previously, and suggests it results from short-range dynamical correlations between the Ce ions, mediated by itinerant \textit{f}-electrons via the RKKY interaction. The momentum-space symmetry of the quasielastic response suggests that it stems from the cubic Ce sub-lattice occupying the 8c Wyckoff site, which is responsible for hosting static AFM order below $T_{\mathrm{N}}$, in contrast to the crystallographically inequivalent 4a site which does not appear to contribute magnetically. [Preview Abstract] |
Wednesday, March 4, 2015 4:06PM - 4:18PM |
Q22.00009: Complex T-H phase diagram in Ce3TiSb5 D.E. Jackson, T. Stevenson, D. VanGennep, B. Jones, J.J. Hamlin We have carried out a detailed characterization of single crystals of the hexagonal compound Ce$_{3}$TiSb$_{5}$, via electrical resistivity, magnetization, and specific heat. These results are consistent with Kondo lattice behavior and an antiferromagnetic ordering temperature of 5.5 K. For magnetic fields applied along specific crystallographic orientations, metamagnetic transitions appear and are accompanied by a large negative magnetoresistance. As the temperature is progressively lowered, the metamagnetic transitions bifurcate. [Preview Abstract] |
Wednesday, March 4, 2015 4:18PM - 4:30PM |
Q22.00010: Shubnikov-de Haas Oscillations of filled skutterudite compounds CeOs$_4$Sb$_{12}$ and NdOs$_4$Sb$_{12}$ P.-C. Ho, J. Singleton, F. F. Balakirev, M. B. Maple, T. Yanagisawa The filled skutterudite compounds CeOs$_4$Sb$_{12}$, PrOs$_4$Sb$_{12}$, and NdOs$_4$Sb$_{12}$ are respectively a 1~K antiferromagnetic (AFM) Kondo insulator, a 1.85~K unconventional superconductor (SC), and a 1~K mean-field type ferromagnet (FM). Since SC in PrOs$_4$Sb$_{12}$ exhibits non-BCS properties, it may originate from proximity to AFM and FM quantum-critical points. Therefore, Fermi-surface measurements of NdOs$_4$Sb$_{12}$ and CeOs$_4$Sb$_{12}$ become crucial in understanding the SC pairing mechanism in PrOs$_4$Sb$_{12}$. MHz skin-depth measurements of single crystals of CeOs$_4$Sb$_{12}$ and NdOs$_4$Sb$_{12}$ were performed for temperatures down to 1.3 K and magnetic fields of up to 60 tesla in the Pulsed Field Facility at NHMFL/LANL. Proximity detection oscillator (PDO) data are taken in the 60 tesla generator-driven magnet ($\sim 1$ s) using a rotational probe. Shubnikov-de Haas oscillations were detected for various direction of the magnetic field with respect to the crystalline orientations. The results indicate that NdOs$_4$Sb$_{12}$ has similar Fermi surfaces to those of PrOs$_4$Sb$_{12}$ and LaOs$_4$Sb$_{12}$ but that the Fermi surface of CeOs$_4$Sb$_{12}$ is much different from those of the other three compounds. [Preview Abstract] |
Wednesday, March 4, 2015 4:30PM - 4:42PM |
Q22.00011: Magnetic Structure of the Heavy-fermion Compound CeAuSb$_2$ in Zero-field Guy G. Marcus, Dae-Jeong Kim, Hannoh Lee, Zachary Fisk, Jose A. Rodriguez-Rivera, Collin L. Broholm We have used neutron diffraction to determine the zero-field magnetic structure of the heavy-fermion compound CeAuSb$_2$. Below T$_N\approx 6.2$K, we observe the development of antiferromagnetic Bragg diffraction consistent with previous transport and magnetization measurements. The intensities observed at 7 magnetic satellite locations indicate the staggered magnetization is predominantly along the c-axis. The maximum moment size is $1.15\pm 0.08~\mu_B$ which is large compared with the $0.4~\mu_B$ moment in the iso-structural heavy fermion ferromagnet CeAgSb$_2$. This suggests that the antiferromagnetic CeAuSb$_2$ is deeper into a magnetic phase. The spin structure, due mainly to the Ce-4f sites, is described as a transverse polarized spin density wave with an incommensurate component of the wave vector in the basal plane. We will discuss these results and bulk measurements in terms of an ANNNI model and effective near neighbor exchange interactions. [Preview Abstract] |
Wednesday, March 4, 2015 4:42PM - 4:54PM |
Q22.00012: Structural and physical properties of new Ce-based silicides CeMAl4Si2 (M$ = $ Rh, Ir, Pt) and germanides Nirmal Ghimire, Filip Ronning, Darrick Williams, Brian Scott, Yongkang Luo, Samantha Cary, Thomas Albrecht-Schmitt, Joe Thompson, Eric Bauer There is a great deal of interest in the Ce-based intermetallic compounds because of the wide variety of strongly correlated electron behavior they exhibit including heavy Fermion behavior, quantum criticality, unconventional superconductivity and complex magnetic order. Recently we have synthesized new Ce-based tetragonal layered silicides - CeMAl$_{4}$Si$_{2}$ (M$=$Rh, Ir, Pt) that show anisotropic behavior in magnetic susceptibility and electrical resistivity. Furthermore, electronic structure calculations reveal a quasi 2D-character of the Fermi surface. We will discuss the importance of these observations and relevance of these and the related compounds in search of new heavy fermion superconductors.~ We will also present the structural and physical properties of the related Ce-based tetragonal/hexagonal germanides. [Preview Abstract] |
Wednesday, March 4, 2015 4:54PM - 5:06PM |
Q22.00013: ABSTRACT WITHDRAWN |
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