Effects of crystal texture on exchange anisotropy in NiO spin valves

The effects of crystal texture on magnetoresistance, exchange anisotropy field H-ex and coercive field H-c in the NiO350 Angstrom/NiFe50 Angstrom/Cu-20 Angstrom/NiFe50 Angstrom spin valve films deposited on Coming glass, MgO(100), MgO(110), and MgO(111) by rf and dc magnetron sputtering techniques were investigated. The H-ex and H-c of the NiO350 Angstrom/NiFe50 Angstrom bilayers grown on MgO(111) and Coming glass were almost the same 90-93 Oe and 56-60 Oe, respectively. The H-ex of the bilayer film on MgO(100) decreased to 68 Oe, however, the H-c of that increased to 114 Oe. The steplike magnetoresistance curve of the spin valve film on MgO(110) disappeared. The x-ray scan of the NiO film deposited on Coming glass shows weakly preferred crystal orientation of NiO(200), (111) and (220) texture, and the NiO films on the MgO single crystals have been grown (100), (110), and (111) epitaxial textures. These results show that there is no clear trend of increasing H-ex for films with greater (111) texture. The large H-c of the bilayer on MgO(100) is probably due to interface roughness. (C) 1997 American institute of Physics.