Spin gap in the single spin-12 chain cuprate Sr1.9Ca0.1CuO3

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

doi:10.1103/PhysRevB.89.184410

Spin gap in the single spin-12 chain cuprate Sr1.9Ca0.1CuO3

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

DOI 10.1103/PhysRevB.89.184410 · Physical Review B

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Abstract

We report Cu63 nuclear magnetic resonance and muon spin rotation measurements on the S=1/2 antiferromagnetic Heisenberg spin chain compound Sr1.9Ca0.1CuO3. An exponentially decreasing spin-lattice relaxation rate T1−1 indicates the opening of a spin gap. This behavior is very similar to what has been observed for the cognate zigzag spin chain compound Sr0.9Ca0.1CuO2, and it confirms that the occurrence of a spin gap upon Ca doping is independent of the interchain exchange coupling J′. Our results therefore suggest that the appearance of a spin gap in an antiferromagnetic Heisenberg spin chain is induced by a local bond disorder of the intrachain exchange coupling J. A low-temperature upturn of T1−1 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.