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 Ni/sub 50/Fe/sub 50//Ni/sub 81/Fe/sub 19/ 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 Ni/sub 50/Fe/sub 50/ and Ni/sub 81/Fe/sub 19/ layers. The Ni/sub 81/Fe/sub 19/ layer has the effect of forcing the domain structure in the Ni/sub 50/Fe/sub 50/ layer towards a flux closure structure through exchange coupling.