Regensburg 2016 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 3: Correlated Electrons: Frustrated Magnets - Pyrochlore Systems and Iridates

TT 3.1: Vortrag

Montag, 7. März 2016, 09:30–09:45, H20

Persistent spin dynamics in NaCaCo₂F₇ as evidenced by µSR — •Sascha Albert Bräuninger¹, Rajib Sarkar¹, Jason W. Krizan², Shanu Dengre¹, Philipp Materne¹, Christopher Baines³, Hubertus Luetkens³, Robert J. Cava², and Hans-Henning Klauss¹ — ¹Institute for Solid State Physics, TU Dresden, D-01069, Germany — ²Department of Chemistry, Princeton University, Princeton, NJ 08544, USA — ³Laboratory for Muon-Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen, Switzerland

The fluoride pyrochlore NaCaCo₂F₇ is a newly discovered frustrated pyrochlore with a frustration index of f = |θ_CW|/T_f≈ 56. While recent NMR experiments on NaCaCo₂F₇ suggested a spin frozen state below 3 K, neutron scattering experiments on the other hand proposed XY like antiferromagnetic spin clusters at low energies. We present µSR studies on NaCaCo₂F₇. Present results indicate the slowing down of the magnetic (spin) fluctuations upon cooling towards the NMR and neutron scattering spin frozen state temperature of T_sf≈ 3.0 K. The µSR relaxation rate increases slightly below this frozen state, and remains constant down to 20 mK. In the µSR window there is no indication of static magnetism in NaCaCo₂F₇. In longitudinal field (100-4000 G) the relaxation rate do not vary indicating that the spin fluctuations are dynamic, and this is persistent even at T≈ 20 mK. While persistent spin dynamics (PSD) appears to be a generic feature of frustrated magnetic systems, it is not clear so far for the present case whether this is associated with quantum fluctuations, spin-liquid physics, or some other effect.