Berlin 2015 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 67: Correlated Electrons: f-Electron Systems

TT 67.8: Vortrag

Mittwoch, 18. März 2015, 17:00–17:15, H 3005

Momentum-space structure of quasielastic spin fluctuations in Ce₃Pd₂₀Si₆ — •P. Y. Portnichenko¹, A. S. Cameron¹, M. A. Surmach¹, P. P. Deen^2,3, S. Paschen⁴, A. Prokofiev⁴, J.-M. Mignot⁵, A.M. Strydom⁶, M.T.F. Telling^7,8, A. Podlesnyak⁹, and D. S. Inosov¹ — ¹TU Dresden, Germany — ²ESS, Sweden — ³Univ. of Copenhagen, Denmark — ⁴Vienna Univ. of Technology, Austria — ⁵LLB, France — ⁶Univ. of Johannesburg, South Africa — ⁷ISIS, UK — ⁸Univ. of Oxford, UK — ⁹SNS, USA

Among heavy-fermion metals, Ce₃Pd₂₀Si₆ is one of the heaviest-electron systems known to date. Using high-resolution neutron spectroscopy, we observed low-energy magnetic scattering from a single crystal of this compound in the paramagnetic state. We investigated its temperature dependence and distribution in Q space. At low temperatures, a quasielastic magnetic response persists with varying intensity all over the Brillouin zone. It forms a broad hump centered at the (111) scattering vector, surrounded by minima of intensity at (002), (220) and equivalent wave vectors. The Q-space structure distinguishes this signal from a simple crystal-field excitation and rather lets us ascribe it to short-range dynamical correlations between the neighboring Ce ions, mediated by the itinerant heavy f-electrons via the RKKY mechanism. Upon heating, the energy width of the signal follows the conventional T^1/2 law, Γ(T)=Γ₀+A√T. The Q-space symmetry of the quasielastic response suggests that it stems from the simple-cubic Ce sublattice occupying the 8c Wyckoff site, whereas the inequivalent 4a site remains magnetically silent.