Single write poles tend to large shape anisotropy which results in a very
large remnant field when not actually writing. This has now been
eliminated by giving the write pole the form of a three layer laminate in
which two ferromagnetic layers are separated by a non-magnetic or
antiferromagnetic coupling layer. Strong magnetostatic coupling between
the outer layers causes their magnetization directions to automatically
be antiparallel to one another, unless overcome by the more powerful
write field, leaving the structure with a low net magnetic moment. The
thickness of the middle layer must be carefully controlled.