Phase stabilization in FexMn100−x thin films in an effect of Mn composition and deposition temperature

In this work, phase stabilization in epitaxial Fe x Mn 100−x thin films formed on MgO(1 0 0) substrates is investigated in dependence on Mn content and deposition temperature. With a wide variety of compositions (50 ≤ x ≤ 100) and growth temperatures (from 30 °C to 400 °C), high-quality films were effectively produced, demonstrating a considerable sensitivity of structural and magnetic characteristics on both Mn content and deposition conditions. When the Mn content reached x= 30 under low-temperature growth (30 °C), a structural phase transition was observed from the ferromagnetic α-Fe phase (a ≈ 2.867 Å) to an ordered α-bcc FeMn alloy with a significantly larger lattice constant (a ≈ 8.69 Å). Consequently, magnetism gradually decreased as the concentration of Mn increased, which is consistent with the Slater-Pauling behavior of transition metal alloys. Notably, the α-bcc FeMn alloy phase had weak thermal stability, and at high growth temperatures (between 100 °C and 450 °C), the α-Fe phase reappeared. These results provide a useful framework for customizing magnetic and structural features for spintronic and magnetic device applications, as well as important insights into the interaction of composition, temperature, and phase evolution in FeMn thin films.