Structural comparisons of ion beam and dc magnetron sputtered spin valves by high‐resolution transmission electron microscopy

We have used high‐resolution transmission electron microscopy to compare the nanostructures of ion‐beam and dc magnetron sputter‐deposited giant magnetoresistive (GMR) spin valves and to correlate nanostructure with magnetic properties. Very low coercivities and strong exchange bias (<8 Oe, 125 Oe) were achieved in ion‐beam‐deposited spin valves of the form NiFe(50)/Co(20)/Cu(≳25)/Co(20)/NiFe(50)/FeMn(150)/Ta(30 A); these were compared with typical dc magnetron deposited structures of the same kind, both with and without a Ta seed layer, which exhibited similar and poorer exchange biasing but superior GMR ratios (to 8%.) Cross‐sectional and plane‐view samples were prepared of all three structures and examined by high‐resolution electron microscopy. Near‐perfect (111)‐textured fcc metal and c‐axis hcp Co columnar grains were revealed in the ion beam deposited sample, while some (10°) dispersion of this texture and random grain orientations were observed in the Ta‐seeded and unseeded dc magnetron sputter‐de...