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Hole Doping Effects on Spin-gapped Na2Cu2TeO6 via Topochemical Na Deficiency

K. Morimoto·Y. Itoh·K. Yoshimura·M. Kato·K. Hirota
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Abstract

We report the magnetic susceptibility and NMR studies of a spin-gapped layered compound Na2Cu2TeO6 (the spin gap $Δ\sim$ 250 K), the hole doping effect on the Cu2TeO6 plane via a topochemical Na deficiency by soft chemical treatment, and the static spin vacancy effect by nonmagnetic impurity Zn substitution for Cu. A finite Knight shift at the $^{125}$Te site was observed for pure Na2Cu2TeO6. The negative hyperfine coupling constant $^{125}A_{tr}$ is an evidence for the existence of a superexchange pathway of the Cu-O-Te-O-Cu bond. It turned out that both the Na deficiency and Zn impurities induce a Curie-type magnetism in the uniform spin susceptibility in an external magnetic field of 1 T, but only the Zn impurities enhance the low-temperature $^{23}$Na nuclear spin-lattice relaxation rate whereas the Na deficiency suppresses it. A spin glass behavior was observed for the Na-deficient samples but not for the Zn-substituted samples. The dynamics of the unpaired moments of the doped holes are different from that of the spin vacancy in the spin-gapped Cu2TeO6 planes.

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K. Morimoto, Y. Itoh, K. Yoshimura, M. Kato, K. Hirota. 2006-07-05. Hole Doping Effects on Spin-gapped Na2Cu2TeO6 via Topochemical Na Deficiency. https://doi.org/10.1143/jpsj.75.083709

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