Bulletin of the American Physical Society
2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009; Pittsburgh, Pennsylvania
Session A34: Superconductivity: Spin Properties |
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Sponsoring Units: DCMP Chair: John Tranquada, Brookhaven National Laboratory Room: 404 |
Monday, March 16, 2009 8:00AM - 8:12AM |
A34.00001: Evidence for Local Moment Magnetism in Superconducting Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta }$ John Tranquada, G.Y. Xu, G.D. Gu, M. Huecker, B. Fauque, T.G. Perring, C. Stock, L.-P. Regnault We have used inelastic neutron scattering to measure the dynamic spin susceptibility in optimally-doped Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta }$ (T$_{c}$ = 91 K). Four crystals with a total mass of 19 g were measured on the MAPS spectrometer at ISIS for temperatures of 10 K and 100 K. We have been able to identify the magnetic excitations in the energy range 20-90 meV. The magnetic nature of the scattering has been confirmed with spin-polarization analysis on IN22 at the ILL. While we see temperature-dependent changes for energies around 40 meV that are consistent with earlier studies, we find that the Q-integrated signal shows a much weaker variation with temperature. The absolute magnetic cross section is quite comparable to that of spin fluctuations in stripe ordered La$_{1.875}$Ba$_{0.125}$CuO$_{4}$. As the magnetism in the latter system has been shown to have a dominant contribution from local moments [1], we argue that the same must be true for Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta }$. [1] M. Huecker et al., Phys. Rev. B (accepted); cond-mat/0503417v3. [Preview Abstract] |
Monday, March 16, 2009 8:12AM - 8:24AM |
A34.00002: Phase Separation and Magnetism in High Temperature Superconductors Samuel Emery, Barret Wells, Joseph Budnick, William Hines, Linda Udby, Niels Hessel Anderson, Kim Lefmann, Christof Niedermayer, Fangcheng Chou Previous work by our group has determined that the low temperature phase diagram of super-oxygenated, La2CuO4 consists of only a few line phases that are either superconducting (SC) or magnetic. Samples with doping levels between the stable phases will segregate into separate domains; this raises the question as to the nature of the interaction between SC and magnetic domains. The application of a magnetic field has been shown to enhance the magnetic scattering associated with a spin density wave order parameter. In our phase separated samples, the magnitude of this enhancement varies strongly with no apparent dependence on hole concentration or phase fractions. Disorder in cuprate superconductors also seems to favor magnetic order over superconducting order, and may be responsible for the variations we find. We present muon and neutron results of the enhancement of magnetic order by magnetic field and oxygen disordering in superoxygenated La2-xCuO4+y. [Preview Abstract] |
Monday, March 16, 2009 8:24AM - 8:36AM |
A34.00003: Stripe order in $\bf La_{2-x}Ba_{x}CuO_4$ at ambient and high pressure. M. Huecker, J. S. Wen, Z. J. Xu, G. D. Gu, J. M. Tranquada, M. v. Zimmermann The pronounced stability of the charge and spin stripe order in $\rm La_{2-x}Ba_{x}CuO_4$ at $\rm x=1/8$ doping still is a poorly understood peculiarity. A combination of electronic and structural interactions is likely, however it has been difficult to clearly separate the involved mechanisms. One approach is to explore how stripe order fades away for dopings $\rm x \neq 1/8$. We have performed high energy (100 keV) x-ray diffraction and static magnetization experiments on single crystals between x=0.095 and 0.155. To our surprise, at ambient pressure stripes exist in a much broader range of doping around $\rm x=1/8$ than expected. In the underdoped region charge stripe order always coincides with a structural transition associated with a rotation of the octahedral tilt axis. However, for $\rm x=1/8$ and high pressure we have been able to show that stripe order also occurs in the absence of this structural phase, which motivates us to discuss stripes in terms of an electronic liquid crystal phase. [Preview Abstract] |
Monday, March 16, 2009 8:36AM - 8:48AM |
A34.00004: The local magnetic field response of $\mathrm{La_{2-x}Sr_{x}CuO_{4}}$ on the overdoped side of the phase diagram as revealed by $\mathrm{\mu SR}$ G.J. MacDougall, A.A. Aczel, S.-J. Kim, J.A. Rodriguez, C.R. Wiebe, G.M. Luke, T. Ito, P.L. Russo, A.T. Savici, Y.J. Uemura, H. Kim, S. Wakimoto, R.J. Birgeneau There is now a large body of evidence from local probes which point to intrinsic heterogeneity in the cuprates. One example is the recent reports of an inhomogenous magnetic field response in the underdoped materials, as revealed by muon spin rotation experiments. In an effort to explore this field response, we have measured the $\mathrm{/mu SR}$ spectra of $\mathrm{La_{2-x}Sr_{x}CuO_{4}}$ in a number of applied magnetic fields and with $x$ ranging from the underdoped to heavily overdoped materials. I will summarize these efforts, and present the resultant data in the context of existing literature. Possible interpretations and directions for future research will be discussed. [Preview Abstract] |
Monday, March 16, 2009 8:48AM - 9:00AM |
A34.00005: The emergence of coherent magnetic excitations in the pseudogap state of underdoped superconducting La$_{2-x}$Sr$_{x}$CuO$_{4}$ S.M. Hayden, O.J. Lipscombe, B. Vignolle, T.G. Perring, C.D. Frost We use inelastic neutron scattering to measure the magnetic
excitations in the underdoped superconductor
La$_{2-x}$Sr$_{x}$CuO$_{4}$ (x=0.085, $T_c$=22~K) over wider
energy ($5 |
Monday, March 16, 2009 9:00AM - 9:12AM |
A34.00006: Spin Excitations in La$_{1.75}$Sr$_{0.25}$Zn$_{0.01}$Cu$_{0.99}$O$_{4}$ Stephen Wilson, B. K. Freelon, Z. Yamani, W. Buyers, C. Rotundu, S. Wakimoto, Robert Birgeneau Recently, reports of a dramatic enhancement in the dynamic, incommensurate, spin density wave response in overdoped La$_{2-x}$Sr$_{x}$Cu$_{1-y}$Zn$_{y}$O$_{4}$ [PRB \textbf{72}, 064521 (2005)] have provided considerable insight toward the microscopic understanding of Zn-induced magnetic states and their interaction with the superconducting phase. As a continuation of these studies, in this talk we will present our recent inelastic neutron scattering studies of spin excitations within the Zn-doped cuprate, La$_{1.75}$Sr$_{0.25}$Zn$_{0.01}$Cu$_{0.99}$O$_{4 }$(LSCZO x=0.25, y=0.01). The dispersion of the spin density wave excitations throughout the Brillouin zone will be presented along with the local spin susceptibility from $\Delta $E=0-45meV. Particular focus will be given to the modifications in the magnetic behavior induced via Zn-substitution in this overdoped LSCZO system. [Preview Abstract] |
Monday, March 16, 2009 9:12AM - 9:24AM |
A34.00007: Magnetic signatures of the pseudogap phase and doping dependence of the antiferromagnetic resonance in HgBa$_{2}$CuO$_{4+\delta }$ Yuan Li, Victor Baledent, Neven Barisic, Philippe Bourges, Yongchan Cho, Benoit Fauque, Klaudia Hradil, Richard Mole, Yvan Sidis, Guichuan Yu, Xudong Zhao, Martin Greven We present our latest experimental results for the pseudogap phase of the model high-Tc superconductor HgBa$_{2}$CuO$_{4+\delta }$. Refinement of our polarized neutron diffraction experiments [Y. Li \textit{et al.}, Nature \textbf{455}, 372 (2008)] using sizable single-crystals of this structurally simple compound consistently show a novel magnetic order below the pseudogap temperature. Furthermore, DC magnetic susceptibility measurements on the highest-quality crystals exhibit a response with highly anisotropic temperature- and doping-dependence, in which the pseudogap anomaly is only visible when the magnetic field is applied along the $c$-axis. These findings strongly suggest that the new magnetic order competes with the superconductivity. Building on our initial work for optimally-doped HgBa$_{2}$CuO$_{4+\delta }$ [G. Yu \textit{et al., }arXiv: 0810:5759], we also briefly discuss preliminary results for the doping dependence of the antiferromagnetic resonance. [Preview Abstract] |
Monday, March 16, 2009 9:24AM - 9:36AM |
A34.00008: Spin correlations and magnetic excitation spectrum of electron-doped Nd$_{2-x}$Ce$_{x}$CuO$_{4\pm \delta }$ near the magnetic quantum critical point Eugene Motoyama, Guichuan Yu, Yuan Li, Daniel Petitgrand, Klaudia Hradil, Richard Mole, Patrick Mang, Inna Vishik, Owen Vajk, Martin Greven One of the most intriguing issues in the field of high-T$_{c}$ superconductivity is the electron-hole asymmetry: the hole- or electron-doping of the parent Mott insulators leads to superconductors with differing properties. For the comparatively less-studied electron-doped materials, the antiferromagnetic phase extends much further with doping and appears to overlap with the superconducting phase. Our previous inelastic neutron scattering measurements show that in the compound Nd$_{2-x}$Ce$_{x}$CuO$_{4\pm \delta }$, genuine long-range antiferromagnetism does not extend as far as previously thought, and may not coexist with bulk superconductivity; the system features a magnetic quantum critical point at x$\sim $0.13, very close to the composition above which superconductivity is first observed [Motoyama \textit{et al.}, Nature \textbf{445}, 186 (2007)]. Here we present new measurements for the instantaneous spin correlations and the magnetic excitation spectrum that aim to refine our understanding of the physics in this interesting doping regime. [Preview Abstract] |
Monday, March 16, 2009 9:36AM - 9:48AM |
A34.00009: Studies of broken time reversal symmetry states in high temperature superconductors using high resolution Sagnac interferometry Elizabeth Schemm, Hovnatan Karapetyan, Jing Xia, Martin M. Fejer, Aharon Kapitulnik Using a cryogenic fiber Sagnac interferometer, we measure polar Kerr effect to high precision in several high-$T_c$ superconductors, concentrating on $\mathrm{YBa_2Cu_3O}_{6+x}$. Previous work on $\mathrm{YBa_2Cu_3O}_{6+x}$ showed non-zero Kerr rotations on the order of $\sim$ 1 $\mu$rad, appearing near the pseudogap temperature $T^*$ and marking what appears to be a true phase transition. We continue this study on single crystals and oriented films to further understand the dependence of the observed Kerr signal on crystal direction, as well as to further probe the anomalous response of this effect to magnetic field training. [Preview Abstract] |
Monday, March 16, 2009 9:48AM - 10:00AM |
A34.00010: Giant impact of magnetic impurity on stability of stripe order in high-Tc cuprate Masaki Fujita, Masanori Enoki, Satoshi Iikubo, Kazuyoshi Yamada To study the stability of stripe orders in cuprate oxides thought impurity-effect, we performed neutron-scattering experiments on La$_{1.88-y}$Sr$_{0.12+y}$Cu$_{1- y}$M$_{y}$O$_4$ ($y$=0 for M=Cu, Zn and $y$=0.01 for M=Ga, Fe). Well-defined incommensurate peaks from charge-density-wave order was induced in the low- temperature-orthorhombic phase (LTO) by impurity substitution, and the scattering intensity is much stronger in the Fe-doped system than in the Zn-doped one. Integrated intensity of magnetic peak from spin-density-wave order was also enhanced by Fe-doping, while it does not change so much by Zn -and Ga- substitutions. These results indicate that the static spin and charge stripe orders can be realized in the LTO phase, and the stability is effectively induced by doping the magnetic impurity. [Preview Abstract] |
Monday, March 16, 2009 10:00AM - 10:12AM |
A34.00011: Anomalous normal state magneto-resistance in the noncentrosymmetric superconductor Li$_{2}$Pt$_{3}$B B. J. Taylor, C. McElroy, T. A. Sayles, A. C. Mota, M. Brian Maple The isotypic superconducting compounds Li$_{2}$Pd$_{3}$B and Li$_{2}$Pt$_{3}$B crystallize in a structure lacking physical inversion symmetry. In contrast to the inversion symmetry breaking superconductors CePt$_{3}$Si, CeRhSi$_{3}$, and UIr, to date, no evidence of magnetic order has been reported in either Li$_{2}$Pd$_{3}$B or Li$_{2}$Pt$_{3}$B. Through detailed magnetoresistive and magnetization measurements of Li$_{2}$Pt$_{3}$B, we have observed behavior suggestive of a link between normal state electronic transport and magnetic behavior, and properties of the superconducting ground state. Corresponding changes in magnetoresistive and magnetic behavior are found wherein both properties exhibit two distinct features at high and intermediate temperatures. Remarkably, both features evolve as a function of magnetic field and temperature towards the $T$ = 0 value of the superconducting upper critical field H$_{c2}$(0)~$\approx $~1.5 T. Polycrystalline samples of Li$_{2}$Pt$_{3}$B with the highest reported values to date of the superconducting critical temperature, T$_{c}$ = 3K , and residual resistivity ratio, RRR $\approx $ 2, were used in this study. [Preview Abstract] |
Monday, March 16, 2009 10:12AM - 10:24AM |
A34.00012: Glassy effects in magnetotransport in La$_{1.97}$Sr$_{0.03}$CuO$_4$ thin films X. Shi, J. Jaroszy\'nski, D. Popovi\'c, C. Panagopoulos, G. Logvenov, A. Bollinger, I. Bozovic We have studied the in-plane magnetoresistance (MR) in atomically smooth, MBE grown La$_{1.97}$Sr$_{0.03}$CuO$_4$ thin films. The MR was measured at temperatures between 0.6~K and 8~K and in $B$ up to 9~T, both parallel and perpendicular to the $c$-axis. The MR exhibits strong dependence on magnetic field history, such as hysteresis and memory at low $T$, similar to the results on $c$-axis transport in single crystal samples [1]. Here, however, the difference between field-cooled and zero-field cooled MR vanishes above $T \sim$ 5~K, independent of the magnitude and orientation of $B$. Low $T$ resistance noise measurements also will be discussed. The results suggest that the glassiness observed in the films may also originate from the slow charge dynamics at low temperatures. [1] I. Rai\v{c}evi\'c, \emph{et. al.}, PRL \textbf{101}, 177004 (2008). [Preview Abstract] |
Monday, March 16, 2009 10:24AM - 10:36AM |
A34.00013: Novel positive magnetoresistance in lightly doped La$_{2}$CuO$_4$ I. Rai\v{c}evi\'c, D. Popovi\'c, C. Panagopoulos, T. Sasagawa We have measured magnetoresistance (MR) in single crystals of La$_{1.97}$Sr$_{0.03}$CuO$_4$ and La$_{2}$Cu$_{0.97}$Li$_{0.03}$O$_4$ at temperatures 0.050$\leq T$(K)$\leq 70$ and fields $0\leq B$(T)$\leq 18$ parallel and perpendicular to the c-axis. Our study reveals an unusual, low-field positive MR in both in-plane and c-axis transport in both materials and for both \emph{B} orientations. However, while the positive c-axis MR may persist up to \emph{T} as high as 40 K, the large positive in-plane MR occurs only at very low $T\ll T_{sg}$ ($T_{sg}$ -- spin glass transition temperature). In that regime, where the noise spectroscopy disclosed slow and correlated charge dynamics [1], both the in-plane and c-axis positive MR exhibit signatures of glassiness, such as memory and hysteresis. We discuss the possible mechanism responsible for this novel low-field positive MR that appears to be intimately related to the emergence of the charge glass dynamics. [1] I. Rai\v{c}evi\'c \textit{et al.}, Phys. Rev. Lett. \textbf{101}, 177004 (2008). [Preview Abstract] |
Monday, March 16, 2009 10:36AM - 10:48AM |
A34.00014: Magnetic hysteresis studies of Tl-2223 substituted by Fe and Zn Aly Abou-Aly, Ramadan Awad, Ibrahim Ibrahim, Ahmed Faraj Effect of Fe and Zn substitutions on the magnetic hysteresis of Tl-2223 are investigated in high magnetic fields up to 9 Tesla and at different temperatures (T= 6, 20, 40 and 80 K). The results of magnetic hysteresis loops show that the area of these loops decreases as Fe-content increases, whereas it increases for Zn-substitutions till x = 0.2 and then decreases for x $>$ 0.2. The magnetization difference $\Delta $M is found to decay exponentially with temperature at low magnetic fields, according to $\Delta $M $\alpha $ exp (-T/T$_{0})$. The characteristic temperature T$_{0}$ is found to be varied from 6 K to 40 K and it is related to the applied magnetic field B according to T$_{0} \quad \alpha $ B$^{-1/n}$. The critical current density is calculated for the prepared samples from magnetic hysteresis measurements and compared with that determined from ac magnetic susceptibility. The results are discussed according to the flux motion and flux pinning. [Preview Abstract] |
Monday, March 16, 2009 10:48AM - 11:00AM |
A34.00015: Neutron Scattering Study of Magnetic Field Effect on the Stripe Order in LBCO Zhijun Xu, Jinsheng Wen, Guangyong Xu, Markus H\"ucker, John Tranquada, Genda Gu We have been investigating the relationship of stripe order to high-temperature superconductivity in cuprates. In particular, our neutron scattering results indicate that spin-stripe order is present in La$_{2-x}$Ba$_{x}$CuO$_{4}$ (LBCO) over a substantial range of doping about x = 1/8, where the bulk superconductivity is anomalously suppressed. Focusing on the x = 1/8 composition, we have recently studied the impact on stripe order of a magnetic field applied along the c-axis [1]. Applying a field up to 7 T, we observed a small enhancement of the intensity of the incommensurate antiferromagnetic superlattice peaks and a slight increase in the ordering temperature. In measurements of the spin dynamics, the field had no significant impact on the small spin gap ($\sim $ 0.5 meV) found in the ordered phase [2]. [1] Jinsheng Wen \textit{et al}., arXiv:0810.4085. [2] J.M. Tranquada \textit{et al}., arXiv:0809.0711. Work supported by Office of Science, U.S. DOE, under Contract No. DEAC02-98CH10886 [Preview Abstract] |
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