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

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 J(k) was determined to be 0.14 erg/cm(2) for IrMn 50 Angstrom. The exchange field (H-ex) decreases rapidly upon heating, resulting in a blocking temperature (T-b) of 250 degrees C. For bottom IrMn based spin valves the exchange bias energy is much higher (J(k)=0.28 erg/cm(2)) while Delta R/R (6.9%) is reduced with respect to top spin valves (> 8.0%). This is interpreted as showing that H-ex is dominantly dependent on fcc(111) crystalline texture while Delta R/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. (C) 2000 American Institute of Physics. [S0021- 8979(00)63208-5].