We report wide-range composition and annealing effects on magnetic properties of Mn x Ga films grown on GaAs (001) by molecular-beam epitaxy. We obtained single-crystalline Mn x Ga films in a surprisingly wide composition range from x=0.76 to 2.6. We show that the magnetism could be effectively tailored by adjusting composition and annealing. Especially, when 0.76≤x≤1.75, Mn x Ga films simultaneously show magnetization from 130 to 450 emu/cc, perpendicular anisotropy among 8.6 to 21 Merg/cc, intrinsic coercivity from 4.38 to 20.1 kOe, normal coercivity up to 3.6 kOe, energy product up to 3.4 MGOe and thermal-stability up to at least 350 o C in contact with GaAs.

A new kind of multifunctional L1(0) -Mn(1.5)Ga film is demonstrated for the first time. These MBE-grown epitaxial films exhibit pronounced magnetic properties at room temperature, including ultrahigh perpendicular coercivity up to 42.8 kOe, giant perpendicular magnetic anisotropy with a maximum of 21.7 Merg/cm(3) and large magnetic energy products up to 2.60 MGOe, which allow various applications in ultrahigh density recording, spintronics, and permanent magnets.

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