PERPENDICULAR MAGNETIC-ANISOTROPY AND MAGNETIC DOMAIN-STRUCTURE IN SPUTTERED EPITAXIAL FEPT(001) L1(0) FILMS

The magnetic domain structure and magnetization curves of chemically o rdered epitaxial FePt(001) films with perpendicular magnetic anisotrop y are discussed. Films were dc magnetron sputtered from a Fe50Pt50 all oy target onto Pt seeded MgO (001) at substrate temperatures of 550 de grees C. The thickness of the FePt layers was varied between 18 and 17 0 nm. Specular and grazing incidence x-ray diffraction measurements co nfirm the presence of the anisotropic, face centered tetragonal (L1(0) ) crystal structure. Long range chemical order parameters of up to 0.9 5 and small mosaic spread, similar to results reported for FePt (001) films grown by molecular beam epitaxy. For film thicknesses greater th an or equal to 50 nm in-plane and out-of-plane hysteresis measurements indicate large perpendicular magnetic anisotropies and at the same ti me low (about 10%) perpendicular remanence. Magnetic force microscopy reveals highly interconnected perpendicular stripe domain patterns. Fr om their characteristic widths, which are strongly dependent on the fi lm thickness, a value of the dipolar length D-0 similar to 50 +/- 5 nm is derived. Assuming an exchange constant of 10(-6) erg/ cm, this val ue is consistent with an anisotropy constant K-1 similar to 1 x 10(8) erg/ cc. (C) 1998 American Institute of Physics. [S0021-8979(98)01222- 5].