Magnetic memory device
According to one embodiment, a magnetic memory device includes a first magnetic layer having a variable magnetization direction, a second magnetic layer having a fixed magnetization direction, and a nonmagnetic layer between the first and second magnetic layers. The second magnetic layer includes a first main surface on the nonmagnetic layer side and a second main surface opposite to the first main surface, and includes a first region on the first main surface side and a second region on the second main surface side, and an intermediate region between the first and second regions and containing a predetermined nonmagnetic element. A concentration of the predetermined nonmagnetic element in the intermediate region is higher than that in the first and second regions. The second magnetic layer contains a magnetic element from the first to second main surfaces.
1. A magnetic memory device comprising a stacked structure including a first magnetic layer having a variable magnetization direction; a second magnetic layer having a fixed magnetization direction; and a nonmagnetic layer provided between the first magnetic layer and the second magnetic layer, wherein:
the second magnetic layer includes a first main surface on the nonmagnetic layer side and a second main surface opposite to the first main surface,
the second magnetic layer includes a first region located on the first main surface side, a second region located on the second main surface side, and an intermediate region located between the first region and the second region and containing a predetermined nonmagnetic element, a concentration of the predetermined nonmagnetic element in the intermediate region being higher than that in the first region and that in the second region, and
a magnetic element is contained within at least a portion of each of the first region, the second region and the intermediate region of the second magnetic layer from the first main surface to the second main surface thereof, and wherein the intermediate region has a concentration distribution of the predetermined nonmagnetic element in a stacked direction of the stacked structure, and a concentration of the predetermined nonmagnetic element increases to a first point of the concentration distribution and decreases from the first point and increases to a second point of the concentration distribution and decreases from the second point.
2. The magnetic memory device of claim 1 , wherein a concentration of a magnetic element contained in the intermediate region is substantially uniform except for a region near a boundary between the intermediate region and the first region and a region near a boundary between the intermediate region and the second region.
3. The magnetic memory device of claim 1 , wherein the intermediate region has a concentration distribution of a magnetic element in a stacked direction of the stacked structure, and a concentration of the magnetic element decreases to a first point of the concentration distribution and increases from the first point and decreases to a second point of the concentration distribution and increases from the second point.
4. The magnetic memory device of claim 1 , wherein the intermediate region contains a same magnetic element as a magnetic element contained in the first region.
5. The magnetic memory device of claim 1 , wherein the predetermined nonmagnetic element contained in the intermediate region is selected from tantalum (Ta), titanium (Ti), vanadium (V), chromium (Cr), zirconium (Zr), niobium (Nb), molybdenum (Mo), hafnium (Hf), and tungsten (W).
6. The magnetic memory device of claim 1 , wherein a magnetic element contained in the intermediate region is selected from iron (Fe), cobalt (Co), and nickel (Ni).
7. The magnetic memory device of claim 1 , wherein the first region contains iron (Fe) and boron (B).
8. The magnetic memory device of claim 7 , wherein the first region further contains cobalt (Co).
9. The magnetic memory device of claim 1 , wherein the second region contains cobalt (Co) and an element selected from platinum (Pt), nickel (Ni), and palladium (Pd).
10. The magnetic memory device of claim 1 , wherein the intermediate region includes a magnetic region.
11. The magnetic memory device of claim 1 , wherein the intermediate region includes a nonmagnetic region.
12. The magnetic memory device of claim 1 , wherein the first region and the second region have the same magnetization direction as each other.
13. The magnetic memory device of claim 1 , wherein the first magnetic layer contains iron (Fe) and boron (B).
14. The magnetic memory device of claim 13 , wherein the first magnetic layer further contains cobalt (Co).
15. The magnetic memory device of claim 1 , wherein the nonmagnetic layer contains magnesium (Mg) and oxygen (O).
16. The magnetic memory device of claim 1 , wherein the stacked structure further includes a third magnetic layer having a fixed magnetization direction which is antiparallel to the magnetization direction of the second magnetic layer.
17. The magnetic memory device of claim 16 , wherein the third magnetic layer contains cobalt (Co) and an element selected from platinum (Pt), nickel (Ni), and palladium (Pd).
18. The magnetic memory device of claim 1 , wherein a resistance of the stacked structure produced when the magnetization direction of the first magnetic layer is parallel to the magnetization direction of the second magnetic layer is lower than a resistance of the stacked structure produced when the magnetization direction of the first magnetic layer is antiparallel to the magnetization direction of the second magnetic layer.