Growth and magnetic anisotropy of thin W(110)/Co films on Al2O3(11(2)over-bar0) -: art. no. 224415

The growth and magnetism of thin W(110)/Co films deposited by molecular beam epitaxy on single-crystal sapphire Al2O3(11 (2) over bar0) substrates is investigated. Low-energy electron diffraction analysis shows that the Co films grow on the epitaxial W(110) substrate layer with a constant lattice strain up to a Co thickness de, = 20 Angstrom. Pseudomorphic growth is found for the W[1 (1) over bar 0] direction. The thickness-dependent magnetic anisotropy is studied in situ at T = 300 K by means of magneto-optical Kerr-effect measurements on a Co wedge-shaped sample prior and after coverage with a Au overlayer. After the coverage the Co wedge reveals a perpendicular magnetic anisotropy for small Co film thickness followed by a spin-reorientation transition from out-of-plane to in-plane alignment of the magnetization vector in the thickness regime 7 Angstrom less than or equal to d(Co) less than or equal to 9 Angstrom. Spin-dependent neutron reflectivity data provide evidence for a pronounced magnetic anisotropy within the film plane even for relatively thick Co films. The observed decrease of the splitting between spin-up and spin-down reflectivities for decreasing temperature indicates that the spin-reorientation transition of the system W(110)/ Co/Au can also be induced thermally.