Epitaxial ferromagnetic τ-MnAl films on GaAs

We report the growth of epitaxial τ-MnAl ferromagnetic films on GaAs substrates by molecular beam epitaxy (MBE). Reflection high-energy electron diffraction and x-ray diffraction show that the τ-phase films grow with the c axis of the tetragonal unit cell normal to the 100GaAs substrate surface. In the bulk, τ-MnAl is a metastable ferromagnetic phase with uniaxial magnetocrystalline anisotropy. The large hysteresis observed in the Hall resistance versus applied magnetic field suggests that the easy magnetization direction is indeed parallel to the c axis in the MBE-grown films. The growth of these ferromagnetic films with perpendicular magnetization on compound semiconductor substrates creates the possibility of novel devices that combine magnetic memory and magneto-optic functions with semiconductor electronics and photonics.