Structural and microscopic analyses of (α-Fe2O3/Co(NiFe)/Cu/Co(NiFe)) bottom GMR spin valves

The structural and microscopic analyses of Si/α-Fe₂ O₃/Co(NiFe)/Cu/Co(NiFe) bottom GMR spin valves with Co or NiFe free and pinned layers were performed from the point of view of material characteristics. The input sputtering power, substrate bias, and sputtering power source (RF, or DC magnetron) were used as experimental variables. It was confirmed that the crystal structure of α-Fe₂O₃ related to the antiferromagnetic crystalline anisotropy, the surface roughness associated with coupling field (bias field) between the free and the pinned layers through the nonmagnetic Cu layer, and the interdiffusion were crucial factors in determining the GMR performance of Si/α-Fe₂O₃/Co(NiFe)/Cu/Co(NiFe). The increase of Ni-Cu intermixing region due to the Cu interdiffusion was shown to be a much more dominant factor as compared to the interfacial surface roughness in reduction of GMR ratio in α-Fe₂O ₃ bottom spin valve