A magnetoresistance effect element comprises a magnetoresistance effect
film including a magnetically pinned layer whose direction of
magnetization is pinned substantially in one direction, a magnetically
free layer whose direction of magnetization changes in response to an
external magnetic field, and a nonmagnetic intermediate layer located
between the pinned layer and the free layer, and a pair of electrodes
electrically connected to said magnetoresistance effect film to supply a
sense current perpendicularly to a film plane of said magnetoresistance
effect film. The intermediate layer has a first layer including a first
region whose resistance is relatively high and second regions whose
resistance is relatively low. The sense current preferentially flows
through the second regions when the current passes the first layer.
Alternatively, the concentration of oxygen in the first layer may have a
two-dimensional fluctuation, and a first region where the concentration
of oxygen is equal to or higher than 40 atomic % and a second region
where the concentration of oxygen is equal to or lower than 35 atomic %
may be provided in the first layer.