Magnetic force microscopy (MFM) observations have been performed on artificial structures of single-phase Ga0.962Mn0.038N grown by metal organic chemical vapor deposition, showing room-temperature long range magnetic order of Ga0.962Mn0.038N. The MFM results agree well with the theoretical simulation under assumption of uniform magnetization. The ferromagnetism of Ga1−xMnxN is suggested to be closely related to the configuration of Mnn+ and Mn(n+1)+ (n=2,3). This work indicates potential of effectively applying MFM to a variety of weak magnetic epitaxial thin films.