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arXiv · 1403.2890

Spin Gap in the Single Spin-1/2 Chain Cuprate Sr$_{1.9}$Ca$_{0.1}$CuO$_3$

F. Hammerath·E. M. Brüning·S. Sanna·Y. Utz·N. S. Beesetty·R. Saint-Martin·A. Revcolevschi·C. Hess·B. Büchner·H. -J. Grafe
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Abstract

We report $^{63}$Cu nuclear magnetic resonance and muon spin rotation measurements on the S=1/2 antiferromagnetic Heisenberg spin chain compound Sr$_{1.9}$Ca$_{0.1}$CuO$_3$. An exponentially decreasing spin-lattice relaxation rate 1/T$_1$ indicates the opening of a spin gap. This behavior is very similar to what has been observed for the cognate zigzag spin chain compound Sr$_{0.9}$Ca$_{0.1}$CuO$_2$, and confirms that the occurrence of a spin gap upon Ca doping is independent of the interchain exchange coupling $J'$. Our results therefore generally prove the appearance of a spin gap in an antiferromagnetic Heisenberg spin chain induced by a local bond disorder of the intrachain exchange coupling $J$. A low temperature upturn of 1/T$_1$ evidences growing magnetic correlations. However, zero field muon spin rotation measurements down to 1.5 K confirm the absence of magnetic order in this compound which is most likely suppressed by the opening of the spin gap.

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F. Hammerath, E. M. Brüning, S. Sanna, Y. Utz, N. S. Beesetty, R. Saint-Martin, A. Revcolevschi, C. Hess, B. Büchner, H. -J. Grafe. 2014-03-12. Spin Gap in the Single Spin-1/2 Chain Cuprate Sr$_{1.9}$Ca$_{0.1}$CuO$_3$. https://doi.org/10.1103/physrevb.89.184410

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