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

The present work is a comparative study of CoFe/IrMn exchange biased top, b ottom, 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 bl ocking temperature (T-b) of 250 degrees C. For bottom IrMn based spin valve s 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 in terpreted as showing that H-ex is dominantly dependent on fcc(111) crystall ine texture while Delta R/R is sensitive to both crystalline texture and in terface roughness. Dual spin valves based on the above results showed two e xchange loops due to the difference in the exchange bias energy between the top and bottom pinning layers. (C) 2000 American Institute of Physics. [S0 021- 8979(00)63208-5].