Spin-density-functional-based search for half-metallic antiferromagnets

We present results based on local-spin-density calculations of a computational search for half-metallic (HM) antiferromagnetic (AFM) materials within the class of double-perovskite-structure oxides $\mathrm{La}{M}^{\ensuremath{'}}{M}^{\ensuremath{''}}{\mathrm{O}}_{3}$ that incorporate open-shell $3d$ (or $4d)$ transition-metal ions ${M}^{\ensuremath{'}}{,M}^{\ensuremath{''}}$. The pairs ${M}^{\ensuremath{'}}{M}^{\ensuremath{''}}$=MnCo, CrFe, CrRu, CrNi, MnV, and VCu are studied. Three HM AFM results are found for the (fixed) cubic double perovskite structure. This work provides the first viable candidates for this unusual magnetic phase. ${\mathrm{La}}_{2}$${\mathrm{VMnO}}_{6}$ is the most promising candidate, with the HM AFM phase more stable by 0.17 eV/cell than the ferromagnetic phase. ${\mathrm{La}}_{2}$${\mathrm{VCuO}}_{6}$ is another promising possibility but, because ${\mathrm{V}}^{4+}$ and ${\mathrm{Cu}}^{2+}$ are spin-half ions, quantum fluctuations may play an important role in determining the ground state magnetic and electronic structure. This study indicates that HM AFM materials should not be prohibitively difficult to find.