A magnetoresistance effect devices having a magnetization free layer free
to rotate in an applied magnetic field. The magnetization free layer may
include first and second ferromagnetic material layers with a nonmagnetic
material layer disposed between the two ferromagnetic material layers.
Those ferromagnetic materials are antiferromagnetically coupled with each
other at a magnetic coupling field J (-3 [kOe].ltoreq.J<0 [kOe]) or
ferromagnetically coupled with each other. Alternatively, the
magnetization free film includes a first ferromagnetic material layer
including a center region having a first magnetization and edge regions
having a second magnetization different from the first magnetization and a
second ferromagnetic material layer including a center region having a
third magnetization parallel to the first magnetization and edge regions
having a fourth magnetization different from the third magnetization. In
another embodiment, a roughness at an interface between the first
ferromagnetic material layer and the first nonmagnetic material coupling
layer or an interface between the first second ferromagnetic material
layer and the first nonmagnetic material coupling layer is more than 2
angstroms. Also, the magnetization free layer may be formed of
ferromagnetic material portions ferromagnetically coupled to each other,
or of a nonmagnetic material layer and a first ferromagnetic material
layer having a non-uniform film thickness.
