A current-perpendicular-to-the-plane (CPP) magnetoresistive (MR) sensor
has an improved free layer structure that includes a first ferromagnetic
interface layer on the sensor's nonmagnetic spacer layer, a first
electrically conductive interlayer on the first interface layer, a
central ferromagnetic NiFe alloy free layer on the first interlayer, a
second electrically conductive interlayer on the central free layer, and
a second ferromagnetic interface layer on the second interlayer. The
first ferromagnetic interface layer, central ferromagnetic free layer,
and second ferromagnetic interface layer are ferromagnetically coupled
together across the electrically conductive interlayers so their
magnetization directions remain parallel. The free layer structure may be
used in single or dual CPP sensors and in spin-valve or tunneling MR
sensors.