GMR PROPERTIES OF SPIN VALVES USING MULTILAYERED CO90FE10 FOR FREE MAGNETIC LAYER

To achieve higher GMR ratios in spin valves, Co90Fe10 films were used as the free and the pinned layer. A single layer of CoFe 100 Angstrom and a multilayer of CoFe 18 Angstrom/(Cu 8 Angstrom/CoFe 18 Angstrom)( 5) were used as the free layer. Although the singlelayer CoFe showed l arge coercivities of 58 Oe along the easy axis and 40 Oe along the har d axis, the multilayer CoFe 18 Angstrom/(Cu 8 Angstrom/CoFe 18 Angstro m)(5) showed smaller coercivities of 10 Oe along the easy axis and 1.5 Oe along the hard axis on a 100 Angstrom thick Ta underlayer. The ani sotropy field of the multilayer was 20 Oe. The film structures of the free layer were evaluated and it was found that the multilayer had hig her oriented (111) texture than the single layer. The reason why the m ultilayer had higher oriented (111) texture was that the Cu layers bet ween CoFe layers helped to have highly oriented (111) texture. To redu ce the anisotropy field, the film was annealed in a magnetic field per pendicular to the initial easy axis at several temperatures. As the re sult, the anisotropy field was reduced to 3 Oe and the coercivity was 4 Oe after annealing at 140 degrees C. The GMR ratio of the spin valve of Ta 100 Angstrom/CoFe 18 Angstrom/(Cu 8 Angstrom/CoFe 18 Angstrom)( 4)/Cu 24 Angstrom/CoFe 30 Angstrom/FeMn 150 Angstrom/Ta 50 Angstrom wa s 7% after the annealing. (C) 1996 American Institute of Physics.