Magnetic properties and electronic origin of the interface between dilute magnetic semiconductors with orthogonal magnetic anisotropy

Controlling changes in magnetic anisotropy across epitaxial film interfaces is an important prerequisite for many spintronic devices. For the canonical dilute magnetic semiconductor GaMnAs, magnetic anisotropy is highly tunable through strain and doping, making it a fascinating model system for exploration of anisotropy control in a carrier-mediated ferromagnet. Here, we have used transmission electron microscopy and polarized neutron reflectometry to characterize the interface between GaMnAs-based layers designed to have anisotropy vectors oriented at right angles from one another. For a bilayer of Ga1-xMnxAs1-yPy and Ga1-xMnxAs, we find that the entirety of the Ga1-xMnxAs layer exhibits in-plane magnetic anisotropy and that the majority of the Ga1-xMnxAs1-yPy exhibits perpendicular anisotropy. However, near the Ga1-xMnxAs interface, we observe a thin Mn-rich region of the nominally perpendicular Ga(1-x)A(x)As(1-y)P(y) that instead exhibits in plane anisotropy. Using first-principles energy considerations, we explain this sublayer as a natural consequence of interfacial carrier migration.