MAGNETIC-ANISOTROPY AND MICROSTRUCTURE IN MOLECULAR-BEAM EPITAXIAL FEPT(110) MGO(110)/

We compare the growth, structural, and magnetic properties of FexPt1-x (x similar or equal to 0.6) films grown by molecular beam epitaxy on M gO (110) substrates held at 300 and 500 degrees C. Growth at both temp eratures yields nearly single orientation epitaxial films with FePt, P t [001]//MgO[001] and FePt, Pt (110)//MgO (110). For growth at 300 deg rees C, chemical ordering to the L1(0) (CuAu I) tetragonal phase is in complete (long-range order parameter, S = 0.38) in contrast with growt h at 500 degrees C for which ordering is nearly complete (S = 0.81). D espite incomplete chemical ordering, a large two-fold, in-plane magnet ic anisotropy (K-u = 1.5 X 10(7) erg/cm(3)) is present for the film gr own at 300 degrees C. Transmission electron microscopy for the 300 deg rees C film confirms epitaxial growth with few extended defects but al so reveals that chemical ordering is distributed inhomogeneously withi n the him. The direction of ordering is generally uniform (c axis alon g MgO [001]) but variations in the degree of ordering are evident on a length scale of 1-10 nm. (C) 1998 American Institute of Physics. [S00 21-8979(98)01214-6].