Enhanced film thickness for Néel wall in soft magnetic film by introducing strong magnetocrystalline anisotropy

This study investigated the magnetic domain walls in a single-layer soft magnetic film with strong magnetocrystalline anisotropy energy. The soft magnetic film is composed of a highly c-axis-oriented hcp-Co(81)Ir(19) alloy with strong negative magnetocrystalline anisotropy. The domain structure of the soft Co(81)Ir(19) films with thickness ranging from 50–230 nm in a demagnetization state was observed through magnetic force microscopy and Lorentz transmission electron microscopy. Results reveal that the critical transition thickness at which the domain wall changes from Néel type to Bloch type is about 138 nm, which is much larger than the critical value of traditional Fe- and Co-based soft magnetic films with negligible magnetocrystalline anisotropy. Theoretical calculation was also performed and the calculated result agrees well with experimental data.