Magnetic memory element

1. A magnetic memory element comprising:

a memory layer having magnetic anisotropy on a film surface thereof in a perpendicular direction and in which a magnetization direction is variable;

a reference layer having magnetic anisotropy on the film surface thereof in the perpendicular direction and in which the magnetization direction is fixed; and

a tunnel barrier layer interposed between the memory layer and the reference layer,

wherein the memory layer is made of an alloy including cobalt (Co) and iron (Fe),

wherein a plurality of oxygen atoms are present in an interface between the tunnel barrier layer and the memory layer, and on a surface of the memory layer opposite to the tunnel barrier layer; and

wherein the memory layer includes a plurality of magnetic layers and a plurality of oxygen atoms are present at interfaces between each of the magnetic layers, and a concentration of oxygen is higher at each of the interfaces between the magnetic layers of the memory layer than a concentration of oxygen within each of the magnetic layers of the memory layer.

2. The magnetic memory element according to claim 1 , wherein the tunnel barrier layer is made of an oxide.

3. The magnetic memory element according to claim 2 , wherein the tunnel barrier layer is made of magnesium oxide.

4. The magnetic memory element according to claim 3 , wherein the plurality of oxygen atoms are present in the interface between the tunnel barrier layer and the memory layer in higher concentration than in the tunnel barrier layer.

5. The magnetic memory element according to claim 1 , further comprising a base layer contacting the surface of the memory layer opposite to the tunnel barrier layer.

6. The magnetic memory element according to claim 5 , wherein the base layer is made of nonmagnetic material comprising oxide.

7. The magnetic memory element according to claim 6 , wherein the plurality of oxygen atoms are present in the interface between the base layer and the memory layer in higher concentration than in the base layer.

8. The magnetic memory element according to claim 1 , wherein the tunnel barrier layer is made of magnesium oxide.

9. The magnetic memory element according to claim 1 , wherein each magnetic layer of the memory layer includes magnetic portions formed as columns that extend between adjoining magnetic layers within a nonmagnetic portion that extends between the adjoining magnetic layers.

10. The magnetic memory element according to claim 1 , wherein each magnetic layer of the memory layer includes magnetic portions formed in a granular structure that extends between adjoining magnetic layers within a nonmagnetic portion that extends between the adjoining magnetic layers.

11. A magnetic memory element comprising:

a memory layer having a magnetization direction that is variable;

a reference layer having a magnetization direction that is fixed; and

a tunnel barrier layer interposed between the memory layer and the reference layer,

wherein the memory layer includes a plurality of magnetic layers, each of which is made of an alloy including cobalt (Co) and iron (Fe), and

wherein a plurality of oxygen atoms are present on an interface between the tunnel barrier layer and the memory layer, and on interfaces between each pair of the magnetic layers, and a concentration of oxygen is higher at each of the interfaces between the magnetic layers of the memory layer than a concentration of oxygen within each of the magnetic layers of the memory layer.

12. The magnetic memory element according to claim 11 , further comprising a base layer contacting a surface of the memory layer opposite to the tunnel barrier layer.

13. The magnetic memory element according to claim 12 , wherein a plurality of oxygen atoms are present on an interface between the base layer and the memory layer.

14. The magnetic memory element according to claim 13 , wherein the tunnel barrier layer and the base layer are each made of nonmagnetic material comprising oxide.

15. The magnetic memory element according to claim 14 , wherein the plurality of oxygen atoms are present in the interface between the base layer and the memory layer in higher concentration than in the base layer.

16. The magnetic memory element according to claim 11 , wherein each magnetic layer of the memory layer includes magnetic portions formed as columns that extend between adjoining magnetic layers within a nonmagnetic portion that extends between the adjoining magnetic layers.

17. The magnetic memory element according to claim 11 , wherein each magnetic layer of the memory layer includes magnetic portions formed in a granular structure that extends between adjoining magnetic layers within a nonmagnetic portion that extends between the adjoining magnetic layers.

18. A magnetic memory element comprising:

a memory layer made of an alloy including cobalt (Co) and iron (Fe), having magnetic anisotropy on a film surface thereof in a perpendicular direction and in which a magnetization direction is variable;

a reference layer having magnetic anisotropy on the film surface thereof in the perpendicular direction and in which the magnetization direction is fixed;

a tunnel barrier layer interposed between the memory layer and the reference layer; and

a base layer contacting the surface of the memory layer opposite to the tunnel barrier layer,

wherein a plurality of oxygen atoms are present in an interface between the tunnel barrier layer and the memory layer, and

wherein the memory layer includes magnetic portions formed in a columnar or granular structure that extend between the base layer and the tunnel barrier layer within a nonmagnetic portion that extends between the base layer and the tunnel barrier layer.