L10 MnAl, which is a nonequilibrium ferromagnetic phase, is fabricated successfully with various compositions via high-pressure synthesis. The L10 phase is observed at pressures higher than 5 GPa, indicating that the volume effect is crucial for the stabilization of this phase. The employed synthesis route does not require a Mn-rich ε-phase, which has conventionally been used as the precursor compound. This allows for the synthesis of the L10 phase with a near-stoichiometric composition. In addition to variations in the composition in terms of the Mn/Al ratio, the axial ratio (c/a) as well as the ordering parameter (S) are modified systematically, with the maximum c/a and S values corresponding to the stoichiometric composition. With this structural change, the highest coercive force is also observed at the stoichiometric composition.