Elemental moment variation of bcc Fe_xMn_1−x on MgO(001)

We report the growth, structural characterization, and electronic structure evolution of epitaxially grown bcc Fe_xMn_1−x on MgO(001). It is observed that the 20 nm thick Fe_xMn_1−x alloy films remained bcc from 0.65≤x≤1, much beyond the bulk stability range of 0.88≤x≤1. X-ray absorption spectroscopy and X-ray magnetic circular dichroism show that both the Fe and Mn L₃ binding energies slightly increase with Mn incorporation and that the elemental moment of Fe in the 20 nm crystalline bcc alloy film remain nearly constant, then shows a dramatic collapse near x~0.84. The Mn MCD intensity is found to be small at all compositions that exhibit ferromagnetism - Highlights: • Bcc Fe_xMn_1−x films were stabilized beyond bulk range by epitaxial growth on MgO. • XMCD shows negligible moment in Mn regardless of composition. • Fe moment stays constant until 84% Mn concentration. • Magnetic moment suddenly collapses before any structural change seen in RHEED.