Magnetic compensation and preferential substitution site for Ag in Mn 4 − x Ag x N epitaxial thin films

We report the presence of a magnetic compensation (MC) composition at room temperature in 20 nm thick ${\mathrm{Mn}}_{4\ensuremath{-}x}{\mathrm{Ag}}_x\mathrm{N}$ $(x=0\ensuremath{-}1.0)$ epitaxial thin films prepared on ${\mathrm{SrTiO}}₃(001)$ by molecular beam epitaxy and show that their magnetic structure is significantly altered by Ag doping. Magnetization curves and anomalous Hall effect loops indicate the presence of an MC composition ${x}_{\mathrm{MC}}\ensuremath{\sim}0$.15 at room temperature. X-ray absorption near-edge structure measurements reveal preferential substitution of Ag for Mn atoms at the corner sites. X-ray magnetic circular dichroism measurements show that the magnetic structure changes drastically for $x>{x}_{\mathrm{MC}}$. These results and various considerations suggest that the ${\mathrm{Mn}}_{4\ensuremath{-}x}{\mathrm{Ag}}_x\mathrm{N}$ thin film constitutes a noncollinear magnetic structure above ${x}_{\mathrm{MC}}$. This is significantly different from the previously reported Ni- and Co-doped ${\mathrm{Mn}}₄\mathrm{N}$ epitaxial thin films.