Texture and surface/interface topological effects on the exchange and coercive fields of NiFe/NiO bilayers

The texture and surface/interface topological effects on the exchange held H-ex and coercivity H-c in rf-sputtered NiO/NiFe bilayers were studied. The NiO/NiFe bilayers with NiO crystalline textures of (111), (200), and (220), and different surface/interface roughness, were fabricated by changing the sputtering conditions. The H-ex of the NiO/NiFe bilayers was inversely proportional to the thickness of NiFe. The NiO/NiFe bilayers with different NiO textures of (111) dominant, (200) dominant, or combinations of (111), (200), and (220), respectively, showed almost the same dependence of H-ex on NiFe thickness. Thus, H-ex was insensitive to the texture of NiO films. The surface/interface roughness has a significant effect on H-c of the NiO/NiFe bilayers. By controlling the sputtering process. NiO (45 nm)/NiFe (10 nm) bilayers with a H-ex of 39 Oe, a H-c of 4.1 Oe, and an H-ex/H-c ratio of 9.51 could be obtained. A new parameter of H-ex/H-c was introduced to describe the exchange coupling and coercive properties in ferromagnet/antiferromagnet coupled bilayers. A large H-ex/H-c ratio is very desirable for spin-valve structures. (C) 1997 American Institute of Physics.