Effects of deposition process parameters on exchange coupling of α-Fe2O3/NiFe bi-layers and GMR of α-Fe 2O3/NiFe/Cu/NiFe spin valves

Effects of deposition process parameters on the exchange coupling of α-Fe₂O₃/NiFe bi-layers and GMR characteristics of α-Fe₂O₃/NiFe/Cu/NiFe spin-valves using optimized anti-ferromagnetic α-Fe₂O ₃ layer have been investigated. The exchange bias field was increased in α-Fe₂O₃(50 nm)/NiFe (7 nm) bi-layers by increasing oxygen partial pressure to 14.7%, substrate bias to 125 V, and input sputtering power up to 800 W of RF reactively sputtered α-Fe₂O₃ films. The thickness of NiFe and α-Fe₂O₃ layers also had an influence on the exchange coupling characteristics. By decreasing NiFe thickness from 35 nm to 5 nm and increasing α-Fe₂O₃ thickness from 550 nm, the exchange bias field dramatically increased up to 62.5 Oe. However, in the α-Fe₂O₃ thickness range of 50-100 nm, the exchange bias field decreased from 62.5 to 21.5 Oe. The GMR performance of as-deposited Si/α-Fe₂O₃(50 nm)/NiFe(3.25 nm)/Cu(2 nm)/NiFe(3.25 nm)/Au (5.4 nm) spin valve structures was characterized. The CMR ratio and MR sensitivity was 5.2% and 0.6%/0e, respectively