The magnetoresistance effect element 100 illustrated in FIG. 1 has a “top free-type” structure in which the storage layer 40 is positioned on an upper layer side, and the reference layer 20 is positioned on a lower layer side. However, the magnetoresistance effect element 100 may have a “bottom free-type” structure in which the storage layer 40 is positioned on the lower layer side, and the reference layer 20 is positioned on the upper layer side.

Next, an example of a method for forming the functional layer 43 will be described.

On the interface layer 41, an alloy layer of a selected element of the oxide used in the spin diffusion preventing layer 43a and a magnetic metal element constituting the conductive portions 43b is formed. Subsequently, oxygen is introduced into a chamber wherein the alloy layer has been formed, resulting in oxidation, and a heat treatment is further performed. By such a method, the functional layer 43 having a structure in which a plurality of the conductive portions 43b are surrounded by the spin diffusion preventing layer 43a can be formed.

That is, the energy of formation of the oxide of the selected element is less than the energy of formation of the oxide of the magnetic metal element. Therefore, the spin diffusion preventing layer 43a and the conductive portions 43b can be formed by self-assembly.