  Room temperature ferromagnetism of GaMnN thin films is awaked by a mild
hydrogenation treatment of samples synthesized by molecular beam epitaxy. Local
environment of Mn atoms is monitored by Mn-L2,3 near edge x-ray absorption fine
structure (NEXAFS) technique. Doped Mn ions are present at substitutional sites
of Ga both before and after the hydrogenation. No secondary phase can be
detected. Major valency of Mn changes from +3 to +2 by the hydrogenation. The
present result supports the model that the ferromagnetism occurs when Mn2+ and
Mn3+ are coexistent and holes in the mid- gap Mn band mediate the magnetic
coupling.
