Magnetoresistive element and magnetic memory

1. A magnetoresistive element comprising:

an underlying layer;

a first magnetic layer with a variable magnetization and an easy-axis in a perpendicular direction to a film surface, the first magnetic layer provided on the underlying layer;

a first nonmagnetic layer provided on the first magnetic layers; and

a second magnetic layer with an invariable magnetization and an easy-axis in the perpendicular direction, the second magnetic layer provided on the first nonmagnetic layer,

wherein the underlying layer has a close-packed structure,

the first magnetic layer comprises a ferromagnetic material including CoPd-alloy or CoPt-alloy in which an atomic layer of Co and an atomic layer of Pd or Pt are alternately stacked to an atomically close-packed plane thereof and C-axis directs to the perpendicular direction,

the CoPd-alloy or the CoPt-alloy is oriented in fcc (111)-plane or hcp (0001)-plane, and

a magnetization direction of the first magnetic layer is changed by a bi-directional current flowing through the first magnetic layer, the first nonmagnetic layer and the second magnetic layer.

2. The element of claim 1 ,

wherein the underlying layer includes at least one of Pt, Pd, Ir and Ru.

3. The element of claim 2 ,

wherein the underlying layer has one atomic layer.

4. The element of claim 2 ,

wherein the underlying layer has several atomic layers.

5. The element of claim 1 ,

wherein the first nonmagnetic layer comprises a magnesium oxide.

6. The element of claim 1 , further comprising:

a third magnetic layer which reduces or adjusts a leakage magnetic field from the second magnetic layer; and

a second nonmagnetic layer between the second and third magnetic layers,

wherein the third magnetic layer has an easy-axis in the perpendicular direction.

7. The element of claim 6 ,

wherein saturated magnetization M S2 and a film thickness t 2 of the second magnetic layer and saturated magnetization M S3 and a film thickness t 3 of the third magnetic layer satisfy a relationship of M S2 ×t 2 <M S3 ×t 3 , and

the magnetization directions of the second and third magnetic layers maintain an anti-parallel state.

8. The element of claim 1 , further comprising:

an interface layer between the second magnetic layer and the first nonmagnetic layer,

wherein the interface layer is an alloy (Co 100-x —Fe x ) 100-y B y including Co, Fe and B, where x≦20 at % and 0<y≦30 at %.

9. The element of claim 8 ,

wherein the interface layer has one of a cubic structure and a tetragonal structure, and is (100)-oriented.

10. The element of claim 1 , further comprising:

an interface layer between the first magnetic layer and the first nonmagnetic layer,

wherein the interface layer is an alloy (Co 100-x —Fe x ) 100-y B y including Co, Fe and B, where x≧20 at % and 0<y≦30 at %.

11. The element of claim 10 ,

wherein the interface layer has one of a cubic structure and a tetragonal structure, and is (100)-oriented.

12. The element of claim 1 ,

wherein the first magnetic layer includes nickel (Ni) or vanadium (V).

13. A magnetic memory comprising:

a memory cell array having memory cells,

wherein each of the memory cells comprises:

the element of claim 1 ; and

first and second electrodes sandwiching the element and applying the current to the element.

14. The memory of claim 13 , further comprising:

a first conductive line which is electrically connected to the first electrode;

a second conductive line which is electrically connected to the second electrode; and

a write circuit which is electrically connected to the first and second conductive lines and applies the current to the element.

15. The memory of claim 14 ,

wherein each of the memory cells includes a selective transistor which is electrically connected between the second electrode and the write circuit.