Berlin 2015 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 33: Low-Dimensional Systems: Other Materials
TT 33.1: Vortrag
Dienstag, 17. März 2015, 09:30–09:45, H 3010
NMR on the Antiferromagnetic S=1/2 Heisenberg Spin Chain Sr2CuO3 under the Impact of Ni Impurities — •Yannic Utz1, Franziska Hammerath1, Satoshi Nishimoto1, Stefan-Ludwig Drechsler1, Neela Sekhar Beesetty2, Romuald Saint-Martin2, Alexandre Revcolevschi2, Christian Hess1, Bernd Büchner1, and Hans-Joachim Grafe1 — 1IFW Dresden, Germany — 2SP2M-ICMMO UMR-CNRS, Université Paris-Sud, France
We present 63Cu NMR measurements on single crystals of Sr2CuO3 doped with different amounts of nickel and compare them to numerical DMRG results. The parent compound contains copper-oxygen chains with S=1/2 on the copper site coupled by a large antiferromagnetic exchange coupling J ≈ 2000 K and is known to be a good realization of the 1D Heisenberg model. The measurements show that replacing only a few of the S=1/2 Cu ions with S=1 Ni has a major impact on the magnetic properties of the spin chain system. An unusual line broadening in the low temperature NMR spectra reveals the existence of an impurity-induced local alternating magnetization (LAM), and exponentially decaying spin-lattice relaxation rates T1−1 towards low temperatures indicate the opening of a spin gap similar to Ca-doped Sr2CuO3 [1]. While the T1−1 measurements could be explained by pure chain segmentation, as expected for a S=0 impurity, the spectra can only be understood by taking the nickel.
[1] F. Hammerath et al., Phys. Rev. B 89, 184410 (2014).