Study of exchange anisotropy for Ni80Fe20/Fe60Mn40 (111) epitaxial films

Ni80Fe20/Fe60Mn40 (111) epitaxial films grown on Si(110) buffered by Cu wer e studied systematically by varying the individual layer thicknesses with e mphasis on the detailed structure evolution and its influence on the magnet ic properties. The Cu buffer layer induced epitaxial face-centered-cubic (1 11) growth. Film crystallinity improved as the Cu buffer layer thickness t increased, evidenced from the full width of half maximum of 3.3 degrees for t=1 nm and 1.1 degrees for t = 100 nm. Film surface roughness increased fr om 0.56 to 1.1 nm with increasing Cu buffer layer thickness. The exchange b ias field was around 90 Oe when the Cu buffer layer film thickness was less than 10 nm, higher than the 70 Oe for films with thicker Cu buffer layers. Reversible measurements of the exchange coupling strength were similar to 70 Oe larger than the loop shift for films with Cu buffer layer thickness g reater than 10 nm. For these films the coercivity was larger than 30 Oe. A magnetic force microscope showed a magnetization ripple pattern with a char acteristic length of similar to2 mum, indicating a strong stray field. The angular dependence of exchange bias field for epitaxial films was quite dif ferent from that of polycrystalline films. (C) 2001 American Vacuum Society .