Magnetoresistive element
According to one embodiment, a magnetoresistive element comprises a storage layer having perpendicular magnetic anisotropy with respect to a film plane and having a variable direction of magnetization, a reference layer having perpendicular magnetic anisotropy with respect to the film plane and having an invariable direction of magnetization, a tunnel barrier layer formed between the storage layer and the reference layer and containing O, and an underlayer formed on a side of the storage layer opposite to the tunnel barrier layer. The reference layer comprises a first reference layer formed on the tunnel barrier layer side and a second reference layer formed opposite the tunnel barrier layer. The second reference layer has a higher standard electrode potential than the underlayer.
1. A magnetic random access memory comprising:
a first nonmagnetic layer containing at least one of Hf, Ta, Nb, Al, and Ti;
a first magnetic layer provided on the first nonmagnetic layer and containing a magnetic material;
a second nonmagnetic layer provided on the first magnetic layer and containing O;
a second magnetic layer provided on the second nonmagnetic layer and containing the magnetic material, the magnetic material in the second magnetic layer and the magnetic material in the first magnetic layer being same in concentration; and
a third magnetic layer provided on the second magnetic layer and including Pt or Pd.
2. The memory of claim 1 , wherein the first magnetic layer constitutes a storage layer.
3. The memory of claim 2 , wherein the storage layer has perpendicular magnetic anisotropy with respect to a film plane, and has a variable direction of magnetization.
4. The memory of claim 1 , wherein the second and third magnetic layers constitute a reference layer.
5. The memory of claim 4 , wherein the reference layer has perpendicular magnetic anisotropy with respect to a film plane, and has an invariable direction of magnetization.
6. The memory of claim 1 , wherein the second nonmagnetic layer constitutes a tunnel barrier layer.
7. The memory of claim 1 , wherein an O concentration in the second nonmagnetic layer is higher on the first magnetic layer side than on the second magnetic layer side.
8. The memory of claim 1 , wherein the first nonmagnetic layer has a greater film thickness than the first magnetic layer.
9. The memory of claim 1 , wherein the second nonmagnetic layer contains MgO, Al 2 O 3 , MgAlO, ZnO, or TiO.
10. The memory of claim 1 , wherein the magnetic material in the first magnetic layer and the magnetic material in the second magnetic layer contain Co or Fe.
11. The memory of claim 1 , wherein the third magnetic layer has a greater film thickness than the second magnetic layer.
12. The memory of claim 1 , further comprising first and second electrodes, wherein the first nonmagnetic layer is provided on the first electrode, and the second electrode is provided on the third magnetic layer.
13. The memory of claim 1 , further comprising a fourth magnetic layer provided on the third magnetic layer.
14. The memory of claim 13 , wherein the fourth magnetic layer constitutes a shift cancelling layer.
15. The memory of claim 13 , further comprising a third nonmagnetic layer provided between the third and fourth magnetic layers.
16. The memory of claim 15 , wherein the third nonmagnetic layer contains a conductive material.
17. The memory of claim 16 , wherein the conductive material comprises Ru.
18. The memory of claim 1 , wherein the first nonmagnetic layer further contains at least one of O and N.