#### Abstract

The electronic and magnetic properties of ${\mathrm{K}}_{2}\mathrm{Cu}{\mathrm{P}}_{2}{\mathrm{O}}_{7}$ were investigated by means of susceptibility, specific heat and ${}^{31}\mathrm{P}$ nuclear magnetic resonance (NMR) measurements and by local density approximation (LDA) band structure calculations. The temperature dependence of the NMR shift $K\left(T\right)$ is well described by the $S={\scriptstyle \frac{1}{2}}$ Heisenberg antiferromagnetic chain (HAF) model with nearest neighbor exchange ${J}_{1}\simeq (141\pm 5)\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The corresponding mapping of an LDA-derived tight-binding model leads to ${J}_{1}^{\mathit{LDA}}\simeq 196\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The spin lattice relaxation rate $1/{T}_{1}$ decreases with temperature below $300\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ but becomes nearly temperature independent between 30 and $2\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, as theoretically expected for an $S={\scriptstyle \frac{1}{2}}$ HAF chain. None of the investigated properties give any evidence for long range magnetic order above $2\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, which is in agreement with the results of the band structure calculation, which yield extremely weak exchange to the next nearest neighbor and a very small and frustrated interchain exchange. Thus, ${\mathrm{K}}_{2}\mathrm{Cu}{\mathrm{P}}_{2}{\mathrm{O}}_{7}$ seems to be a better realization of a nearest neighbor $S={\scriptstyle \frac{1}{2}}$ HAF chain than the compounds reported so far.

1 More- Received 7 January 2008

DOI:https://doi.org/10.1103/PhysRevB.77.134451

©2008 American Physical Society