Magnetic memory element and nonvolatile memory device
According to one embodiment, a magnetic memory element includes a stacked body including first and second stacked units stacked with each other. The first stacked unit includes first and second ferromagnetic layers and a first nonmagnetic layer provided therebetween. The second stacked unit includes third and fourth ferromagnetic layers and a second nonmagnetic layer provided therebetween. Magnetization of the second and third ferromagnetic layers are variable. Magnetizations of the first and fourth ferromagnetic layers are fixed in a direction perpendicular to the layer surfaces. A cross-sectional area of the third ferromagnetic layer is smaller than a cross-sectional area of the first stacked unit when cut along a plane perpendicular to the stacking direction.
1. A magnetic memory element comprising: a stacked body,
the stacked body including:
a first stacked unit including:
a first ferromagnetic layer, a magnetization of the first ferromagnetic layer being fixed in a first direction having a component perpendicular to a film surface of the first ferromagnetic layer;
a second ferromagnetic layer being stacked with the first ferromagnetic layer along a stacking direction, a direction of a magnetization of the second ferromagnetic layer being variable in directions perpendicular to a film surface of the second ferromagnetic layer; and
a first nonmagnetic layer provided between the first ferromagnetic layer and the second ferromagnetic layer; and
a second stacked unit stacked with the first stacked unit along the stacking direction, the second stacked unit including:
a third ferromagnetic layer, a direction of a magnetization of the third ferromagnetic layer being variable in directions parallel to a film surface of the third ferromagnetic layer;
a fourth ferromagnetic layer stacked with the third ferromagnetic layer along the stacking direction, a magnetization of the fourth ferromagnetic layer being fixed in a second direction having a component perpendicular to a film surface of the fourth ferromagnetic layer; and
a second nonmagnetic layer provided between the third ferromagnetic layer and the fourth ferromagnetic layer,
a cross-sectional area of the third ferromagnetic layer being smaller than a cross-sectional area of the first stacked unit when cut along a plane perpendicular to the stacking direction,
a direction of the magnetization of the second ferromagnetic layer being set to a direction in accordance with a direction of a current by causing an electron whose spin is polarized by passing the current through the stacked body along the stacking direction to act on the second ferromagnetic layer and by causing a rotating magnetic field generated from a precession of the magnetization of the third ferromagnetic layer to act on the second ferromagnetic layer,
the current being flowed through the first stacked unit and the second stacked unit.
2. The element according to claim 1 , wherein outer edges of the second ferromagnetic layer and the first nonmagnetic layer in the plane include a portion outside an outer edge of the second stacked unit in the plane.
3. The element according to claim 1 , wherein the first direction is opposite to the second direction.
4. The element according to claim 1 , wherein
the stacked body further includes a third nonmagnetic layer provided between the first stacked unit and the second stacked unit and
the third nonmagnetic layer contains at least one nonmagnetic metal selected from the group consisting of copper (Cu), silver (Ag), gold (Au), chromium (Cr), zinc (Zn), gallium (Ga), niobium (Nb), molybdenum (Mo), ruthenium (Ru), palladium (Pd), hafnium (Hf), tantalum (Ta), tungsten (W), platinum (Pt), bismuth (Bi), iridium (Ir), titanium (Ti), and osmium (Os) or an alloy including two or more selected from the group.
5. The element according to claim 1 , wherein
the stacked body further includes a third nonmagnetic layer provided between the first stacked unit and the second stacked unit and
the third nonmagnetic layer contains a metal selected from the group consisting of ruthenium (Ru), tantalum (Ta), tungsten (W), platinum (Pt), palladium (Pd), molybdenum (Mo), niobium (Nb), zirconium (Zr), titanium (Ti), and vanadium (V) or an alloy including at least two selected from the group.
6. The element according to claim 1 , wherein
the stacked body further includes a third nonmagnetic layer provided between the first stacked unit and the second stacked unit,
the third nonmagnetic layer contains a metal selected from the group consisting of ruthenium (Ru), osmium (Os), and iridium (Ir) or an alloy including at least two selected from the group, and
a thickness of the third nonmagnetic layer is not more than 3 nanometers.
7. The element according to claim 1 , wherein the outer edge of the first stacked unit is on an outside of the outer edge of the second stacked unit.
8. The element according to claim 1 , wherein a maximum width of the third ferromagnetic layer along a direction perpendicular to the stacking direction is not more than 0.7 times a maximum width of the first stacked unit along the direction perpendicular to the stacking direction.
9. The element according to claim 1 , wherein the third ferromagnetic layer is amorphous.
10. The element according to claim 1 , further comprising a magnetic shield opposed to at least a part of a side surface of the stacked body.
11. A nonvolatile memory device comprising:
a magnetic memory element including a stacked body,
the stacked body including:
a first stacked unit including:
a first ferromagnetic layer, a magnetization of the first ferromagnetic layer being fixed in a first direction having a component perpendicular to a film surface of the first ferromagnetic layer;
a second ferromagnetic layer being stacked with the first ferromagnetic layer along a stacking direction, a direction of a magnetization of the second ferromagnetic layer being variable in directions perpendicular to a film surface of the second ferromagnetic layer; and
a first nonmagnetic layer provided between the first ferromagnetic layer and the second ferromagnetic layer; and
a second stacked unit stacked with the first stacked unit along the stacking direction, the second stacked unit including:
a third ferromagnetic layer, a direction of a magnetization of the third ferromagnetic layer being variable in directions parallel to a film surface of the third ferromagnetic layer;
a fourth ferromagnetic layer stacked with the third ferromagnetic layer along the stacking direction, a magnetization of the fourth ferromagnetic layer being fixed in a second direction having a component perpendicular to a film surface of the fourth ferromagnetic layer; and
a second nonmagnetic layer provided between the third ferromagnetic layer and the fourth ferromagnetic layer,
a cross-sectional area of the third ferromagnetic layer being smaller than a cross-sectional area of the first stacked unit when cut along a plane perpendicular to the stacking direction,
a direction of the magnetization of the second ferromagnetic layer being set to a direction in accordance with a direction of a current by causing an electron whose spin is polarized by passing the current through the stacked body along the stacking direction to act on the second ferromagnetic layer and by causing a rotating magnetic field generated from a precession of the magnetization of the third ferromagnetic layer to act on the second ferromagnetic layer;
a first interconnection directly or indirectly connected to one of the first ferromagnetic layer and the second ferromagnetic layer; and
a second interconnection directly or indirectly connected to one of the third ferromagnetic layer and the fourth ferromagnetic layer,
the first and second interconnections being configured to flow the current though the first stacked unit and the second stacked unit along the stacking direction.
12. The device according to claim 11 , further comprising a selection transistor provided at least one of between the magnetic memory element and the first interconnection and between the magnetic memory element and the second interconnection.
13. The device according to claim 11 , wherein outer edges of the second ferromagnetic layer and the first nonmagnetic layer in the plane include a portion outside an outer edge of the second stacked unit in the plane.
14. The device according to claim 11 , wherein the first direction is opposite to the second direction.
15. The device according to claim 11 , wherein
the stacked body further includes a third nonmagnetic layer provided between the first stacked unit and the second stacked unit and
the third nonmagnetic layer contains at least one nonmagnetic metal selected from the group consisting of copper (Cu), silver (Ag), gold (Au), chromium (Cr), zinc (Zn), gallium (Ga), niobium (Nb), molybdenum (Mo), ruthenium (Ru), palladium (Pd), hafnium (Hf), tantalum (Ta), tungsten (W), platinum (Pt), bismuth (Bi), iridium (Ir), titanium (Ti), and osmium (Os) or an alloy including two or more selected from the group.
16. The device according to claim 11 , wherein
the stacked body further includes a third nonmagnetic layer provided between the first stacked unit and the second stacked unit and
the third nonmagnetic layer contains a metal selected from the group consisting of ruthenium (Ru), tantalum (Ta), tungsten (W), platinum (Pt), palladium (Pd), molybdenum (Mo), niobium (Nb), zirconium (Zr), titanium (Ti), and vanadium (V) or an alloy including at least two selected from the group.
17. The device according to claim 11 , wherein
the stacked body further includes a third nonmagnetic layer provided between the first stacked unit and the second stacked unit,
the third nonmagnetic layer contains a metal selected from the group consisting of ruthenium (Ru), osmium (Os), and iridium (Ir) or an alloy including at least two selected from the group, and
a thickness of the third nonmagnetic layer is not more than 3 nanometers.
18. The device according to claim 11 , wherein the outer edge of the first stacked unit is on an outside of the outer edge of the second stacked unit.
19. The device according to claim 11 , wherein a width of the third ferromagnetic layer along a direction perpendicular to the stacking direction is not more than 0.7 times a width of the first stacked unit along the direction perpendicular to the stacking direction.
20. The device according to claim 11 , wherein the third ferromagnetic layer is amorphous.