Chemical Manipulation of High- TC Ferromagnetism in ZnO Diluted Magnetic Semiconductors

We report the use of targeted $p$- and $n$-type chemical perturbations to manipulate high-${T}_{mathrm{C}}$ ferromagnetism in ${mathrm{Mn}}^{2+}ensuremath{mathbin:}mathrm{ZnO}$ and ${mathrm{Co}}^{2+}ensuremath{mathbin:}mathrm{ZnO}$ in predictable and reproducible ways. We demonstrate a clear correlation between nitrogen and high-${T}_{mathrm{C}}$ ferromagnetism for ${mathrm{Mn}}^{2+}ensuremath{mathbin:}mathrm{ZnO}$ and an inverse correlation for ${mathrm{Co}}^{2+}ensuremath{mathbin:}mathrm{ZnO}$, both as predicted by recent theoretical models. These chemical perturbations reveal rich possibilities for exerting external control over high-${T}_{mathrm{C}}$ spin ordering in diluted magnetic semiconductors.