Evidence for Impurity Effects in Metal Chain Compounds: The Electron Paramagnetic Resonance of "Extrinsic" Magnus's Green Salt

Electron-paramagnetic-resonance studies of the "one-dimensional" metal-chain compound Magnus's green salt, ${\mathrm{P}\mathrm{t}\left(\mathrm{N}{\mathrm{H}}_3\right)}_4$Pt${\mathrm{Cl}}_4$, has revealed the presence of localized hole states having an axial resonance with $g_{\parallel }=1.939\mathrm{}\pm 0.002$ and $g_{\perp }=2.504\mathrm{}\pm 0.002$. These states have been identified as bound $d_{z^2}$-like states associated with a $d_{z^2}$-like valence band. From the observed hyperfine pattern we infer that the holes, although localized, have orbits extended over several Pt sites along the chain. We show how the states can be introduced in a series of doping experiments with Magnus's green salt powders.