Control of the asymmetric band structure in Mn2Au by a ferromagnetic driver layer

Hard x-ray angle-resolved photoemission spectroscopy reveals the momentum-resolved band structure in an epitaxial ${\mathrm{Mn}}_2\mathrm{Au}$(001) film capped by a 2-nm-thick ferromagnetic permalloy layer. By magnetizing the permalloy capping layer, the exceptionally strong exchange bias aligns the Néel vector in the ${\mathrm{Mn}}_2\mathrm{Au}$(001) film accordingly. Uncompensated interface Mn magnetic moments in ${\mathrm{Mn}}_2\mathrm{Au}$ were identified as the origin of the exchange bias using x-ray magnetic circular dichroism in combination with photoelectron emission microscopy. Using time-of-flight momentum microscopy, we measure the asymmetry of the band structure, $E\left(k\right)\ne E(-k)$, in ${\mathrm{Mn}}_2\mathrm{Au}$ resulting from the homogeneous orientation of the Néel vector. Comparison with theory shows that the Néel vector, determined by the magnetic moment of the top Mn layer, is antiparallel to the permalloy magnetization. The experimental results demonstrate that hard x-ray photoemission spectroscopy can measure the band structure of epitaxial layers beneath a metallic capping layer and corroborate the asymmetric band structure in ${\mathrm{Mn}}_2\mathrm{Au}$ that was previously inferred only indirectly.