Chemical Manipulation of High-TCFerromagnetism 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 ${\mathrm{Mn}}^{2+}:\mathrm{ZnO}$ and ${\mathrm{Co}}^{2+}:\mathrm{ZnO}$ in predictable and reproducible ways. We demonstrate a clear correlation between nitrogen and high-$T_{\mathrm{C}}$ ferromagnetism for ${\mathrm{Mn}}^{2+}:\mathrm{ZnO}$ and an inverse correlation for ${\mathrm{Co}}^{2+}:\mathrm{ZnO}$, 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.