Magnetoresistance memory device

1. A magnetoresistance memory device, comprising:

a memory cell including:

a first ferromagnetic layer, a direction of magnetization of the first ferromagnetic layer remaining unchanged when data is read or written from or into the memory cell;

a tunnel barrier layer above the first ferromagnetic layer;

a second ferromagnetic layer above the tunnel barrier layer;

a third ferromagnetic layer above the second ferromagnetic layer, the third ferromagnetic layer including an oxide of an alloy including iron; and

a fourth ferromagnetic layer above the third ferromagnetic layer, the fourth ferromagnetic layer including iron and a 5d transition metal, and a direction of magnetization of the fourth ferromagnetic layer being changeable by writing data into the memory cell.

2. The device according to claim 1 , wherein the 5d transition metal includes at least one of lutetium, hafnium, tantalum, tungsten, rhenium, osmium, iridium, or platinum.

3. The device according to claim 2 , wherein the alloy is an alloy of iron and a metal having an atomic number smaller than an atomic number of the 5d transition metal.

4. The device according to claim 3 , wherein the third ferromagnetic layer is on the second ferromagnetic layer, and the fourth ferromagnetic layer is on the third ferromagnetic layer.

5. The device according to claim 4 , wherein the second ferromagnetic layer includes iron and boron.

6. The device according to claim 5 , wherein the metal is at least one of rhodium, titanium, zirconium, cobalt, boron, vanadium, niobium, chromium, molybdenum, silicon, scandium, yttrium, gadolinium, magnesium, or aluminum.

7. The device according to claim 1 , wherein the 5d transition metal includes at least one of iridium or platinum.

8. The device according to claim 7 , wherein the alloy is an alloy of iron and a metal having an atomic number smaller than an atomic number of the 5d transition metal.

9. The device according to claim 8 , wherein the third ferromagnetic layer is on the second ferromagnetic layer, and the fourth ferromagnetic layer is on the third ferromagnetic layer.

10. The device according to claim 9 , wherein the second ferromagnetic layer includes iron and boron.

11. The device according to claim 10 , wherein the metal is at least one of rhodium, titanium, zirconium, cobalt, boron, vanadium, niobium, chromium, molybdenum, silicon, scandium, yttrium, gadolinium, magnesium, or aluminum.

12. The device according to claim 7 , wherein the third ferromagnetic layer is on the second ferromagnetic layer, and the fourth ferromagnetic layer is on the third ferromagnetic layer.

13. The device according to claim 1 , wherein the alloy is an alloy of iron and a metal having an atomic number smaller than an atomic number of the 5d transition metal.

14. The device according to claim 13 , wherein the third ferromagnetic layer is on the second ferromagnetic layer, and the fourth ferromagnetic layer is on the third ferromagnetic layer.

15. The device according to claim 14 , wherein the second ferromagnetic layer includes iron and boron.

16. The device according to claim 15 , wherein the metal is at least one of rhodium, titanium, zirconium, cobalt, boron, vanadium, niobium, chromium, molybdenum, silicon, scandium, yttrium, gadolinium, magnesium, or aluminum.

17. The device according to claim 1 , wherein the third ferromagnetic layer is on the second ferromagnetic layer, and the fourth ferromagnetic layer is on the third ferromagnetic layer.

18. The device according to claim 17 , wherein the second ferromagnetic layer includes iron and boron.

19. The device according to claim 1 , wherein the second ferromagnetic layer includes iron and boron.

20. The device according to claim 1 , wherein the alloy is an alloy of iron and at least one of rhodium, titanium, zirconium, cobalt, boron, vanadium, niobium, chromium, molybdenum, silicon, scandium, yttrium, gadolinium, magnesium, or aluminum.