  MnxGa films with high perpendicular anisotropy, coercivity and energy product
have great application potential in ultrahigh-density perpendicular recording,
permanent magnets, spin-transfer-torque memory and oscillators,
magneto-resistance sensors and ferromagnetic metal/semiconductor
heterostructure devices. Here we present a comprehensive diagram of effective
magnetism-tailoring of perpendicularly magnetized MnxGa films grown on III-V
semiconductor GaAs by using molecular-beam epitaxy for the first time, by
systematically investigating the wide-range composition and detailed
post-growth annealing effects. We show that the (001)-orientated MnxGa films
with L10 or D022 ordering could be crystallized on GaAs in a very wide
composition range from x=0.76 to 2.6. L10-ordered MnxGa films show robust
magnetization, high remanent ratio, giant perpendicular anisotropy, high
intrinsic and extrinsic coercivity, and large energy product, which make this
kind of material favorable for perpendicular magnetic recording,
high-performance spintronic devices and permanent magnet applications. In
contrast, D022-ordered films exhibit lower perpendicular anisotropy and weaker
magnetism. Post-growth annealing MnxGa films studies reveal high
thermal-stability up to 450 oC, and effective tailoring of magnetic properties
can be realized by prolonging annealing at 450 oC. These results would be
helpful for understanding this kind of material and designing new spintronic
devices for specific practical applications.
