CoFe/IrMn exchange biased top, bottom, and dual spin valves

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Abstract
The present work is a comparative study of CoFe/IrMn exchange biased top, bottom, and dual spin valves. For as-deposited top spin valves the exchange bias energy Jk was determined to be 0.14 erg/cm2 for IrMn 50 Å. The exchange field (Hex) decreases rapidly upon heating, resulting in a blocking temperature (Tb) of 250 °C. For bottom IrMn based spin valves the exchange bias energy is much higher (Jk=0.28 erg/cm2) while ΔR/R (6.9%) is reduced with respect to top spin valves (>8.0%). This is interpreted as showing that Hex is dominantly dependent on fcc(111) crystalline texture while ΔR/R is sensitive to both crystalline texture and interface roughness. Dual spin valves based on the above results showed two exchange loops due to the difference in the exchange bias energy between the top and bottom pinning layers.