Nitrogen-induced magnetic transition in small chromium clusters

Abstract

Using density functional theory with generalized gradient approximation for exchange and correlation, we show that otherwise antiferromagnetically coupled chromium atoms in very small chromium clusters couple ferromagnetically when doped with a nitrogen atom, thus leading to giant magnetic moments. For example, the magnetic moment of ${\mathrm{Cr}}_2\mathrm{N}$ is found to be ${\text{9μ}}_{\mathrm{B}}$ while that of ${\mathrm{Cr}}_2$ is ${\text{0μ}}_{\mathrm{B}}.$ Strong bonding between Cr and N atoms brings about this magnetic transition. The Cr atoms nearest neighbor to N couple ferromagnetically with each other and antiferromagnetically with nitrogen. The significance of these results in understanding the ferromagnetic order in Cr-doped GaN is discussed.