Magnetic exchange bias enhancement through seed layer variation in FeMn/NiFe layered structures

The exchange bias and crystalline texture of the multilayer structure (Ta/Al/seed/Fe₅₀Mn₅₀/Ni₈₁Fe₁₉/Al₂O₃/Ni₈₁Fe₁₉/Al/Ta with seed=Ni₈₁Fe₁₉ or Ni₈₁Fe₁₉/Cu) has been characterized. Measurements indicate an abrupt decrease in exchange bias of the Ni₈₁Fe₁₉ pinned layer for samples with very thin seed layers, and exchange bias as high as 325 Oe for thicker seed layers. Fluctuation of exchange bias with thickness was greatly reduced for the Ni₈₁Fe₁₉/Cu seed configuration. X-ray diffraction measurements demonstrate a correlation between exchange bias and strong (1 1 1) texture of FeMn. The results suggest a high sensitivity of Ni₈₁Fe₁₉ roughness and texture on deposition conditions, and corroborate previous observations of roughness in ultrathin NiFe films.