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

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Abstract
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 (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‐deposited samples, respectively. No amount of the α‐FeMn (A12) phase was observed in any of the films. Exchange bias strengths and coercivity of the top Co/NiFe/FeMn layers thus correlate strongly with the degree of (111) texture.