Berlin 2012 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 45: Correlated Electrons: Poster Session
TT 45.67: Poster
Donnerstag, 29. März 2012, 15:00–19:00, Poster B
NMR evidence for peculiar spin gaps in a doped S=1/2 Heisenberg spin chain — •Yannic Utz1, Christian Rudisch1, Franziska Hammerath1, Hans-Joachim Grafe1, Ashwin Mohan1, Surjeet Singh2, Romuald Saint-Martin3, Alexandre Revcolevschi3, Patrick Ribeiro1, Christian Hess1, Anja Wolter1, Vladislav Kataev1, Satoshi Nishimoto1, Stefan-Ludwig Drechsler1, and Bernd Büchner1 — 1IFW Dresden, Germany — 2Indian Institute of Science Education and Research, Pune, India — 3Laboratoire de Physico-Chimie de l’Etat Solide, Université Paris-Sud, Orsay, France
We present 63Cu Nuclear Magnetic Resonance (NMR) measurements on undoped, Ca-doped and Ni-doped SrCuO2 single crystals. SrCuO2 is a good realization of a one-dimensional S=1/2 Heisenberg spin chain. This is manifested by the theoretically-expected temperature-independent NMR spin-lattice relaxation rate T1−1.
In Sr0.9Ca0.1CuO2 an exponential decrease of T1−1 below 90 K evidences the opening of a gap in the spin excitation spectrum, which amounts to Δ= 50 K [1]. DMRG calculations are presented to discuss the origin of this spin gap. New results on SrCu0.99Ni0.01O2 also indicate the presence of a spin gap, which is twice as large as in Sr0.9Ca0.1CuO2, despite the minor doping level of Ni compared to Ca.
We discuss different possible impacts of Ca (S=0) and Ni (S=1) doping on structural and magnetic properties of the parent compound.
F. Hammerath et al., Phys. Rev. Lett. 107, 017203 (2011).