Effects of deposition process parameters on exchange coupling of α-Fe2O3/NiFe Bi-layers and GMR of α-Fe2O3/NiFe/Cu/NiFe spin valves

Effects of deposition process parameters on the exchange coupling of alpha -Fe2O3/NiFe bi-layers acid GMR characteristics of alpha -Fe2O3/NiFe/Cu/NiFe spin-valves using optimized anti-ferromagnetic alpha -Fe2O3 layer have been investigated. The exchange bias field was increased in alpha -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 alpha -Fe2O3 films, The thickness of NiFe and alpha -Fe2O3 layers also had an influence on the exchange coupling characteristics. By decreasing NiFe thickness from 35 nm to 5 nm and increasing alpha -Fe2O3 thickness from 5-50 nm, the exchange bias field dramatically increased up to 62.5 Oe, However, in the alpha -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/ alpha -Fe2O3(50 nm)/NiFe(3.25 nm)/Cu(2 nm)/ NiFe(3.25 nm)/ Au (5.4 nm) spin valve structures was characterized. The GMR ratio and MR sensitivity was 5.2% and 0.6%/Oe, respectively.