Bulletin of the American Physical Society
APS March Meeting 2010
Volume 55, Number 2
Monday–Friday, March 15–19, 2010; Portland, Oregon
Session J34: Correlated Electrons: New Materials |
Hide Abstracts |
Sponsoring Units: GMAG Chair: Eric Bauer, Los Alamos National Laboratory Room: E144 |
Tuesday, March 16, 2010 11:15AM - 11:27AM |
J34.00001: Unconventional magnetic field tuned quantum ground states in the noncentrosymmetric compound Yb$_{2}$Fe$_{12}$P$_{7}$ Ryan Baumbach, James Hamlin, Lei Shu, Diego Zocco, M. Brian Maple, Jim O'Brien, Pei -Chun Ho Although so-called non-Fermi-liquid (NFL) behavior has been intensely investigated, there is no consensus as to its origin. A well known scenario for NFL behavior is the quantum critical point (QCP) model, where a second order phase transition (usually antiferromagnetic) is suppressed to $T$ = 0 K by a control parameter. NFL behavior is found near the QCP, after which FL behavior is recovered for larger tuning parameter values. We will discuss the unusual phase diagram in single crystals of the noncentrosymmetric compound Yb$_{2}$Fe$_{12}$P$_{7}$, which exhibits a crossover from a zero magnetic field NFL ground state to another distinct NFL quantum region which is stabilized with magnetic field. Interestingly, the transition between the two states coincides with the suppression of antiferromagnetism towards $T$ = 0 K. Based on these observations, we argue that a fundamental understanding of QCP and NFL phenomena and their interrelationship has yet to be realized. [Preview Abstract] |
Tuesday, March 16, 2010 11:27AM - 11:39AM |
J34.00002: Magnetic, electronic and structural properties of the filled skutterudite EuFe$_{4}$As$_{12}$ Andreas Leithe-Jasper, Walter Schnelle, Helge Rosner, Miriam Schmitt, Yuri Prots, Angela Trapananti, Cornelius Strom, Yuri Grin The europium iron arsenide EuFe$_{4}$As$_{12}$ with filled skutterudite structure has been synthesized and its structural, electronic, magnetic and thermodynamic properties have been investigated. The Fe and Eu moments order ferrimagnetically at T$_{C}$ = 151 K, the highest magnetic ordering temperature among filled skutterudite compounds. LDA band structure calculations confirm the observed magnetic polarizations and suggest that the conduction electrons in EuFe$_{4}$As$_{12}$ have a large spin polarization, albeit lower than in the isostructural EuFe$_{4}$Sb$_{12}$. We present a comparative study of the electronic and magnetic properties for both compounds, including the isostructural EuFe$_{4}$P$_{12}$, where the exchange of the pnictide can be considered as chemical pressure. To separate the influence of mere volume effects and a change of the pnictide we also studied the behaviour under hydrostatic pressure for EuFe$_{4}$As$_{12}$, both experimentally and theoretically. [Preview Abstract] |
Tuesday, March 16, 2010 11:39AM - 11:51AM |
J34.00003: Surface State Modification of XRu$_{2}$Si$_{2}$, X=(La, Ce, Th, U) J.D. Denlinger, O. Krupin, B.J. Kim, J.W. Allen, K. Haule, Kyoo Kim, G. Kotliar, J.L. Sarrao, N.P. Butch, M.B. Maple The three-dimensional electronic structures of heavy fermion f-electron materials XRu$_{2}$Si$_{2}$ X=(Ce,U) and their non-f reference materials (X=La,Th) are investigated using photon-dependent angle-resolved photoemission spectroscopy (ARPES). The spatial-dependences of the characterization of UHV-cleaved surfaces combined with guidance from theoretical surface slab calculations clearly identify surface termination related features resulting from cleavage between X-Si layers. Experimental ARPES results are shown for various adsorbate and dosing experiments that suppress or modify the surface states via Si adatom bonding or charge transfer. These results greatly aid the clear identification of the true bulk bands. Differences in the surface state electronice structures between X=(La,Ce, Th, U) arise mainly from different band fillings related to the valence of the bulk X atom. [Preview Abstract] |
Tuesday, March 16, 2010 11:51AM - 12:03PM |
J34.00004: Superconductivity of PrPt$_4$Ge$_{12}$ and LaPt$_4$Ge$_{12}$ filled skutterudite compounds Walter Schnelle, Michael Nicklas, Helge Rosner, Andreas Leithe-Jasper, Roman Gumeniuk, Yuri Grin, Peter Thalmeier, Alexander Maisuradze, Rustem Khasanov, Alex Amato Among the recently discovered rare-earth filled skutterudites $R$Pt$_4$Ge$_{12}$ ($R$ = La--Nd, Sm, Eu) there are two superconducting compounds - LaPt$_4$Ge$_{12}$ and PrPt$_4$Ge$_{12}$ [1]. In the latter Pr is in a well-separated singlet crystal field ground state. This allows for a rather high $T_c$ of 7.9\,K - comparable to the $T_c$ = 8.3\,K of LaPt$_4$Ge$_{12}$. By muon spin rotation and specific heat measurements a superconducting gap with point nodes and time-reversal symmetry (TRS) breaking is found below $T_c$ for PrPt$_4$Ge$_{12}$ while the La compound does not show TRS breaking [2,3]. Interestingly, samples of Pr$_x$La$_{1-x}$Pt$_4$Ge$_{12}$ have very similar $T_c$. We discuss the implications of these observations for the superconducting order parameters of these compounds.\newline [1] R.Gumeniuk et al., Phys.Rev.Lett. 100, 017002 [2] A.Maisuradze et al., Phys.Rev.Lett. 103, 147002 [3] A.Maisuradze et al., submitted [Preview Abstract] |
Tuesday, March 16, 2010 12:03PM - 12:15PM |
J34.00005: Neutron scattering studies of ferromagnetic superconductor UGe$_{2}$ under pressure D.A. Sokolov, A.D. Huxley, R. Ritz, C. Pfleiderer, T. Keller Observation of an unconventional superconductivity in ferromagnetic UGe$_{2}$ when ferromagnetism is suppressed by pressure indicates a dramatic modification of its electronic structure near the Quantum Critical Point [1]. We present high resolution measurements of the lattice constants of ferromagnetic superconductor UGe$_{2}$ under pressure probed by a novel technique, which utilizes Larmor precession of polarized neutrons and surpasses the resolution of conventional scattering methods by an order of magnitude. We have observed sharp anomalies at the Curie temperature, T$_{C}$ and at T$_{X}$, which marks the crossover regime. Our studies under pressure of 10, and 12 kbar indicate that the sharp anomaly corresponding to T$_{C}$ shifted to lower temperature in agreement with a phase diagram. At the pressure corresponding to an onset of superconductivity, 10kbar, the lattice expansion corresponding to ferromagnetic transition undergoes a first order transition and increases by a factor of 3. The results indicate a complex response of the electronic structure of UGe$_{2}$ to external pressure and suggest a strong magnetoelastic coupling as one of multiple energy scales that stabilize superconductivity in UGe$_{2}$. [1] S. S. Saxena, et al., Nature 406, 587 (2000) [Preview Abstract] |
Tuesday, March 16, 2010 12:15PM - 12:27PM |
J34.00006: Near-Fermi level band renormalization effects in f electron systems Tomasz Durakiewicz, Yinwan Li, Peter S. Riseborough, Peter M. Oppeneer, John J. Joyce, Eric D. Bauer, Kevin S. Graham High energy and momentum resolution Angle Resolved Photoemission (ARPES) was used to analyze the near-Fermi level features in the electronic structure of 4f and 5f systems: CeIrIn$_5$, Ce$_2$IrIn$_8$, USb$_2$ and UPd$_2$Al$_3$. Small, but measureable kinks in the dispersion of both 4f and 5f electron bands are interpreted as signatures of interactions with bosonic modes as well as electron-electron interactions. Effects of hybridization and interband scattering on the electronic structure are found and discussed. Temperature - dependent ARPES is used to trace and characterize the changes in the near-Fermi level electronic structure related to the emergence of coherent quasiparticles. [Preview Abstract] |
Tuesday, March 16, 2010 12:27PM - 12:39PM |
J34.00007: Synthesis, Crystal Structure, and Magnetism of the New UIr$_{4}$Al$_{15}$ Compound Paul Tobash, Filip Ronning, Joe Thompson, Eric Bauer We report on single-crystals of a new compound grown from Al flux, UIr$_{4}$Al$_{15}$, crystallizing in the NdRh$_{4}$Al$_{15.4}$ type structure in the tetragonal space group $P$4$_{2}$/\textit{nmc} (No. 137) with unit cell parameters $a$ = 9.0239(6) {\AA} and $c$ = 15.513(2) {\AA}. The crystal structure of the compound was established from single-crystal X-ray diffraction and was found to be void of any crystallographic disorder. The U atoms center a polyhedron with the coordination number of each U atom being 20. The physical properties of UIr$_{4}$Al$_{15 }$were measured which included magnetic susceptibility, specific heat, and electrical resistivity. The compound was found to undergo long-range antiferromagnetic order at T$_{N}$ = 20 K with a Sommerfeld coefficient extrapolated in the antiferromagnetically ordered state of \textit{ca}. 42 mJ/mol-K$^{2}$. The physical properties suggest that UIr$_{4}$Al$_{15 }$may be an itinerant antiferromagnet. The compound belongs to a series of isostructural compounds, and preliminary results indicate that Th, La, Ce, Pr, Sm, Yb, and Lu analogues can be synthesized under identical conditions. [Preview Abstract] |
Tuesday, March 16, 2010 12:39PM - 12:51PM |
J34.00008: Electronic and magnetic properties of the uranium and plutonium dipnictides R. C. Albers, Jian-Xin Zhu, S. Rudin, M. D. Jones, A. K. McMahan, J. M. Wills First-principles electronic structure calculations have been performed for uranium and plutonium dipnictides based on density functional theory. The magnetism in these compounds is investigated first with spin-polarization only and then also with an orbital-polarization correction. It is found that the inclusion of the orbital-polarization correction improves the comparison between theory and experiment. The Fermi surface topology and the determination of extremal orbitals are also presented. [Preview Abstract] |
Tuesday, March 16, 2010 12:51PM - 1:03PM |
J34.00009: Structural and magnetic properties of LnNiGa4 (Ln = Y, Gd-Yb) Yi Li, Kandace Thomas, Richard Hembree, Amar Karki, David Young, John Ditusa, Jiandi Zhang, Julia Chan Rare earth intermetallic compounds often display a competition between RKKY- and Kondo-type interactions as evident inmagnetic and transport properties. To understand how exchange interactions vary with rare earth elements, we have synthesized and studied a series of LnNiGa4 (Ln = Y, Gd - Tm) compounds. Single crystals of the orthorhombic LnNiGa4 with Cmcm space group symmetry have been grown. Along the crystallographic b-axis, slabs of Ni@Ga7Ln2 and non-magnetic slabs of Ga-only atoms alternate throughout the lattice. Two distinct Ga-sites have been confirmed with X-ray photoelectron spectroscopy. In addition, XPS of TmNiGa4 shows that Ni is in the metallic state. There is a transition from antiferromagnetic to ferromagnetic behavior in the series. The magnetic susceptibility and magnetization measurements reveal magnetic moments larger than expected for a free rare earth ion and is due to conduction electrons contributing to the magnetism. The changes in the Curie-Weiss temperatures are consistent with an RKKY coupling of the magnetic moments. [Preview Abstract] |
Tuesday, March 16, 2010 1:03PM - 1:15PM |
J34.00010: Thermal and magnetic properties of a low-temperature antiferromagnet Ce$_4$Pt$_{12}$Sn$_{25}$ R. Movshovich, N. Kurita, H.-O. Lee, Y. Tokiwa, C.F. Miclea, E.D. Bauer, F. Ronning, J.D. Thompson, P. Ho, M.B. Maple, P. Sengupta, I. Vekhter, Z. Fisk We report specific heat ($C$) and magnetization ($M$) of single crystalline Ce$_4$Pt$_{12}$Sn$_{25}$ at temperature down to $\sim$\,50\,mK and in fields up to 3\,T. $C/T$ exhibits a sharp anomaly at 180\,mK, with a large $\Delta$$C$/$T$\,$\sim$\,30\,J/mol\,K$^2$-Ce, which, together with corresponding the cusp-like magnetization anomaly, indicate antiferromagnetic (AFM) ground state with N\'eel temperature $T_{\mathrm{N}}$\,=\,0.18\,K. Numerical calculations based on Heisenberg model reproduce both specific heat and magnetization data, and point to a very small Kondo scale $T_K$, clearly placing Ce$_4$Pt$_{12}$Sn$_{25}$ in the weak exchange coupling $J < J_c$ limit of the Doniac diagram. Magnetic field suppresses AFM state at $H^* \approx 0.7$ T. Anomalous behavior observed in $M$($H$) vs. $T$ for fields in the vicinity of $H^*$ points to a likely field-induced quantum critical point (QCP) at $H^*$. [Preview Abstract] |
Tuesday, March 16, 2010 1:15PM - 1:27PM |
J34.00011: Critical phenomena in itinerant-electron ferromagnet HfFeGa$_2$ Y. Janssen, C. Marques, L. Wu, K. Park, S.X. Chi, J.W. Lynn, M.C. Aronson Aiming to study quantum critical behavior in itinerant-electron transition-metal ferromagnets, we have recently been first to characterize the intermetallic compound HfFeGa$_2$. We have found that HfFeGa$_2$ is a ferromagnet with a low ordering temperature and a small ordered magnetic moment. We present extensive magnetization and neutron diffraction studies of single crystals of pristine HfFeGa$_2$. ac-magnetization data indicates the Curie temperature T$_{\mathrm{C}}$ $\sim$ 49 K, and above T$_{\mathrm{C}}$ we find Curie-Weiss behavior with an effective moment of $\sim$ 2.2 $\mu_{\mathrm{B}}$/Fe. HfFeGa$_2$ is ferromagnetic with the ordered magnetic moments parallel to the easy $c$-axis of the orthorhombic crystal structure, and with a zero-temperature spontaneous magnetization of $\sim$ 0.6 $\mu_{\mathrm{B}}$/Fe. By a scaling analysis of magnetization and neutron diffraction data we have determined T$_{\mathrm{C}}$ = 48.3 K as well as the critical exponents $\beta = 0.494$ and $\gamma = 1.21$. Our results indicate HfFeGa$_2$ is comparable to the well-known itinerant ferromagnet ZrZn$_2$. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700