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

Abstract

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 ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}{\mathrm{As}}_{1\ensuremath{-}y}{\mathrm{P}}_{y}$ and ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{As}$, we find that the entirety of the ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{As}$ layer exhibits in-plane magnetic anisotropy and that the $majority$ of the ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}{\mathrm{As}}_{1\ensuremath{-}y}{\mathrm{P}}_{y}$ exhibits perpendicular anisotropy. However, near the ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{As}$ interface, we observe a thin Mn-rich region of the nominally perpendicular ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}{\mathrm{As}}_{1\ensuremath{-}y}{\mathrm{P}}_{y}$ that instead exhibits $in\ensuremath{-}plane$ anisotropy. Using first-principles energy considerations, we explain this sublayer as a natural consequence of interfacial carrier migration.