Storage element and storage apparatus
[Object] To provide a storage element and a storage apparatus capable of performing writing operation in a short time without generating write errors. [Solving Means] A storage element includes a layer structure including a storage layer having a direction of magnetization which changes according to information, a magnetization fixed layer having a fixed direction of magnetization, and an intermediate layer disposed therebetween, which intermediate layer contains a nonmagnetic material. The magnetization fixed layer has at least two ferromagnetic layers having a direction of magnetization tilted from a direction perpendicular to a film surface, which are laminated and magnetically coupled interposing a coupling layer therebetween. This configuration may effectively prevent divergence of magnetization reversal time due to directions of magnetization of the storage layer and the magnetization fixed layer being substantially parallel or antiparallel, reduce write errors, and enable writing operation in a short time.
1. A storage element comprising:
a layer structure comprising layers arranged in a lamination direction, the layer structure at least including:
a storage layer having a direction of magnetization to be changed according to information,
a magnetization fixed layer having a fixed direction of magnetization, the magnetization fixed layer including two ferromagnetic layers laminated interposing a coupling layer therebetween, the ferromagnetic layers being magnetically coupled interposing the coupling layer, the ferromagnetic layers having a direction of magnetization tilted from a direction perpendicular to a film surface of at least one of the ferromagnetic layers; and
an intermediate layer containing a nonmagnetic material disposed between the storage layer and the magnetization fixed layer, wherein
the layer structure is configured such that recording of the information is to be performed by current flow in the layer structure in the lamination direction to cause a change in the direction of magnetization of the storage layer.
2. The storage element according to claim 1 , wherein
the magnetization fixed layer includes a first ferromagnetic layer, the coupling layer and a second ferromagnetic layer being laminated in this order,
the first ferromagnetic layer has a first magnetic energy which is defined to have a value calculated by subtracting a magnetic energy in a state where magnetization of the first ferromagnetic layer is perpendicular to its film surface, from a magnetic energy in a state where magnetization of the first ferromagnetic layer is within its film surface,
the second ferromagnetic layer has a second magnetic energy which is defined to have a value calculated by subtracting a magnetic energy in a state where magnetization of the second ferromagnetic layer is perpendicular to its film surface, from a magnetic energy in a state where magnetization of the second ferromagnetic layer is within its film surface, and
the first magnetic energy and the second magnetic energy have values with different signs.
3. The storage element according to claim 2 , wherein
a magnetic coupling energy of the first ferromagnetic layer and the second ferromagnetic layer interposing the coupling layer is defined as an interlayer magnetic coupling energy, and
an absolute value of the interlayer magnetic coupling energy is smaller than an absolute value of twice the value calculated by dividing the product of the first magnetic energy and the second magnetic energy, by the sum of the first magnetic energy and the second magnetic energy.
4. The storage element according to claim 1 , wherein
the magnetization fixed layer further includes an antiferromagnetic layer.
5. The storage element according to claim 4 , wherein
the magnetization fixed layer includes the antiferromagnetic layer, a first ferromagnetic layer, the coupling layer and a second ferromagnetic layer being laminated in this order,
the first ferromagnetic layer has a first magnetic energy which is defined to have a value calculated by subtracting a magnetic energy in a state where magnetization of the first ferromagnetic layer is perpendicular to its film surface, from a magnetic energy in a state where magnetization of the first ferromagnetic layer is within its film surface,
the second ferromagnetic layer has a second magnetic energy which is defined to have a value calculated by subtracting a magnetic energy in a state where magnetization of the second ferromagnetic layer is perpendicular to its film surface, from a magnetic energy in a state where magnetization of the second ferromagnetic layer is within its film surface, and
the first magnetic energy and the second magnetic energy have values with different signs.
6. The storage element according to claim 5 , wherein
magnetization of the antiferromagnetic layer and magnetization of the first ferromagnetic layer are magnetically coupled, and a direction of magnetization of the first ferromagnetic layer within the film surface is fixed.
7. A storage apparatus comprising:
a storage element including a layer structure, the layer structure comprising lavers arranged in a lamination direction, the layer structure at least including:
a storage layer having a direction of magnetization to be changed according to information,
a magnetization fixed layer having a fixed direction of magnetization, the magnetization fixed layer including two ferromagnetic layers laminated interposing a coupling layer therebetween, the ferromagnetic layers being magnetically coupled interposing the coupling layer, the ferromagnetic layers having a direction of magnetization tilted from a direction perpendicular to a film surface of at least one of the ferromagnetic layers; and
an intermediate layer containing a nonmagnetic material disposed between the storage layer and the magnetization fixed layer, wherein
the layer structure is configured such that recording of the information is to be performed by current flow in the layer structure in the lamination direction to cause a change in the direction of magnetization of the storage layer;
a wiring portion configured to supply the current flow; and
a current supply control section configured to control the supply of the current flow via the wiring portion.
8. The storage apparatus according to claim 7 , wherein
the magnetization fixed layer includes a first ferromagnetic layer, the coupling layer and a second ferromagnetic layer being laminated in this order,
the first ferromagnetic layer has a first magnetic energy which is defined to have a value calculated by subtracting a magnetic energy in a state where magnetization of the first ferromagnetic layer is perpendicular to its film surface, from a magnetic energy in a state where magnetization of the first ferromagnetic layer is within its film surface,
the second ferromagnetic layer has a second magnetic energy which is defined to have a value calculated by subtracting a magnetic energy in a state where magnetization of the second ferromagnetic layer is perpendicular to its film surface, from a magnetic energy in a state where magnetization of the second ferromagnetic layer is within its film surface, and
the first magnetic energy and the second magnetic energy have values with different signs.
9. The storage apparatus according to claim 8 , wherein
a magnetic coupling energy of the first ferromagnetic layer and the second ferromagnetic layer interposing the coupling layer is defined as an interlayer magnetic coupling energy, and
an absolute value of the interlayer magnetic coupling energy is smaller than an absolute value of twice the value calculated by dividing the product of the first magnetic energy and the second magnetic energy, by the sum of the first magnetic energy and the second magnetic energy.
10. The storage apparatus according to claim 7 , wherein
the magnetization fixed layer further includes an antiferromagnetic layer.
11. The storage apparatus according to claim 10 , wherein
the magnetization fixed layer includes the antiferromagnetic layer, a first ferromagnetic layer, the coupling layer and a second ferromagnetic layer being laminated in this order,
the first ferromagnetic layer has a first magnetic energy which is defined to have a value calculated by subtracting a magnetic energy in a state where magnetization of the first ferromagnetic layer is perpendicular to its film surface, from a magnetic energy in a state where magnetization of the first ferromagnetic layer is within its film surface,
the second ferromagnetic layer has a second magnetic energy which is defined to have a value calculated by subtracting a magnetic energy in a state where magnetization of the second ferromagnetic layer is perpendicular to its film surface, from a magnetic energy in a state where magnetization of the second ferromagnetic layer is within its film surface, and
the first magnetic energy and the second magnetic energy have values with different signs.
12. The storage apparatus according to claim 11 , wherein
magnetization of the antiferromagnetic layer and magnetization of the first ferromagnetic layer are magnetically coupled, and a direction of magnetization of the first ferromagnetic layer within the film surface is fixed.