The experimental results about structures and properties of FexMn1-x alloys
grown epitaxially on GaAs(001) surface have been reported. For x>0.8, the
Fe(x)Mn(1-)x alloy grows in single crystal line bcc structure, and for x<0.
35, in single crystal line fee structure. But the epitaxial structure is qu
ite complicated when 0.35<x< 0.8, and in this region the epitaxial FexMn1-x
alloy film transforms from ferromagnetic phase to antiferromagnetic one.