Effects of crystal texture on exchange anisotropy in NiO spin valves

Abstract

The effects of crystal texture on magnetoresistance, exchange anisotropy field Hex and coercive field Hc in the NiO350 Å/NiFe50 Å/Cu20 Å/NiFe50 Å spin valve films deposited on Corning glass, MgO(100), MgO(110), and MgO(111) by rf and dc magnetron sputtering techniques were investigated. The Hex and Hc of the NiO350 Å/NiFe50 Å bilayers grown on MgO(111) and Corning glass were almost the same 90–93 Oe and 56–60 Oe, respectively. The Hex of the bilayer film on MgO(100) decreased to 68 Oe, however, the Hc 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 Corning 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 Hex for films with greater (111) texture. The large Hc of the bilayer on MgO(100) is probably due to interface roughness.