Dependence of Exchange Stiffness on Metallic Spacer Layer Material and Thickness in Dual-Interface CoFeB/MgO Magnetic Thin Films

The dependence of exchange stiffness and domain wall width on spacer layer material and thickness in double-layer Co
₂₀
Fe
₆₀
B
₂₀
films is investigated. The exchange stiffness and wall width are inferred from magneto-optic Kerr microscope images of domain structure in conjunction with ferromagnetic resonance spectroscopy and vibrating sample magnetometer measurements of anisotropy and saturation magnetization. Samples include MgO-CoFeB-spacer-CoFeB-MgO films stacks with 0.3 nm, 0.5 nm, or 0.7 nm thick spacer layers consisting of W or Ta. These measurements allow for prediction of the thermal stability factor and nucleation diameter of magnetic tunnel junctions fabricated from these films.