Domain observations of write poles which comprise NiFe double layers by type II contrast electron microscopy

Using the lock-in technique in a scanning electron microscope, we observed the magnetic domain structure of Ni₅₀Fe₅₀/Ni₈₁Fe₁₉ double layer upper write poles of merged type MR heads by changing the electron acceleration voltage. Heads with highest dibit resolution exhibit flux closure domain structure both in Ni₅₀Fe₅₀ and Ni ₈₁Fe₁₉ layers. The Ni₈₁Fe₁₉ layer has the effect of forcing the domain structure in the Ni₅₀ Fe₅₀ layer towards a flux closure structure through exchange coupling