Electric field controllable spin filter tunnel junction magnetoresistive memory devices and methods of making the same
A magnetoresistive memory device includes a first electrode, a second electrode, and a layer stack containing an electric field-modulated magnetic transition layer and a ferroelectric insulator layer located between the first electrode and the second electrode, The electric field-modulated magnetic transition layer includes a non-metallic magnetic material having a ferromagnetic state and a non-ferromagnetic state with a state transition therebetween that depends on an external electric field.
1. A magnetoresistive memory device, comprising:
a first electrode;
a second electrode comprising a ferromagnetic metallic material; and
a layer stack including an electric field-modulated magnetic transition layer and a ferroelectric insulator layer, wherein the electric field-modulated magnetic transition layer includes a non-metallic magnetic material which has a magnetic state transition that depends on an external electric field.
2. The magnetoresistive memory device of claim 1 , wherein the non-metallic magnetic material comprises a semiconductor material or an insulating material.
3. The magnetoresistive memory device of claim 2 , wherein the non-metallic magnetic material comprises a III-V compound semiconductor material.
4. The magnetoresistive memory device of claim 3 , wherein the non-metallic magnetic material comprises manganese-doped gallium arsenide.
5. The magnetoresistive memory device of claim 2 , wherein the non-metallic magnetic material comprises a lanthanide chalcogenide semiconductor material.
6. The magnetoresistive memory device of claim 1 , wherein the non-metallic magnetic material comprises a doped transition metal oxide material.
7. The magnetoresistive memory device of claim 1 , wherein the ferroelectric insulator layer comprises hafnium oxide, zirconium doped hafnium oxide, barium titanate, bismuth ferrite, lead titanate, or lead zirconate titanate.
8. The magnetoresistive memory device of claim 1 , further comprising an antiferromagnetic coupling spacer located on the second electrode.
9. The magnetoresistive memory device of claim 8 , wherein:
the first electrode comprises a nonmagnetic metallic material;
the non-metallic magnetic material has a split conduction band in a ferromagnetic state;
the external electric field is generated by applying a voltage between the first electrode and the second electrode; and
the electric field-modulated magnetic transition layer is configured to function as a tunnel barrier between the first electrode and the second electrode.
10. The magnetoresistive memory device of claim 9 , wherein:
the magnetic state transition that depends on the external electric field comprises a transition between a first state in which a magnetization direction in the lower split conduction band is parallel to a magnetization direction of the second electrode, and a second state in which the magnetization direction in the lower split conduction band is antiparallel to the magnetization of the second electrode.
11. The magnetoresistive memory device of claim 9 , wherein:
the magnetoresistive memory device is in a lower resistance state when the magnetization direction in the lower split conduction band is parallel to a magnetization direction of the second electrode; and
the magnetoresistive memory device is in a higher resistance state when the magnetization direction in the lower split conduction band is antiparallel to a magnetization direction of the second electrode.
12. The magnetoresistive memory device of claim 8 , wherein:
the first electrode comprises a ferromagnetic metallic material which has a lower coercivity than the ferromagnetic metallic material of the second electrode;
the non-metallic magnetic material has a split conduction band in a ferromagnetic state and also has a non-ferromagnetic state with a state transition between the ferromagnetic state and the non-ferromagnetic state that depends on the external electric field;
the external electric field is generated by applying a voltage between the first electrode and the second electrode; and
the electric field-modulated magnetic transition layer is configured to function as a tunnel barrier between the first electrode and the second electrode.
13. The magnetoresistive memory device of claim 12 , wherein:
the magnetoresistive memory device has at least three different magnetoresistive memory states having a different resistance from each other;
the first electrode has a changeable magnetization direction and is configured to function as a free layer; and
the second electrode has a fixed magnetization direction and is configured to function as a reference layer.
14. The magnetoresistive memory device of claim 13 , wherein the magnetoresistive memory device has five magnetoresistive states comprising:
a first magnetoresistive state in which the magnetization direction of the reference layer and the magnetization direction of the free layer are parallel to each other, and the electric field-modulated magnetic transition layer is in the ferromagnetic state in which the magnetization direction in a lower split conduction band is parallel to the magnetization direction of the reference layer;
a second magnetoresistive state in which the magnetization direction of the reference layer and the magnetization direction of the free layer are parallel to each other, and the electric field-modulated magnetic transition layer is in the non-ferromagnetic state;
a third magnetoresistive state in which the magnetization direction of the reference layer and the magnetization direction of the free layer are antiparallel to each other, and the electric field-modulated magnetic transition layer is in the ferromagnetic state in which the magnetization direction in the lower split conduction band is parallel to the magnetization direction of the reference layer;
a fourth magnetoresistive state in which the magnetization direction of the reference layer and the magnetization direction of the free layer are antiparallel to each other, and the electric field-modulated magnetic transition layer is in the non-ferromagnetic state; and
a fifth magnetoresistive state in which magnetization direction of the reference layer and the magnetization direction of the free layer are antiparallel to each other, and the electric field-modulated magnetic transition layer is in the ferromagnetic state in which the magnetization direction in the lower split conduction band is antiparallel to the magnetization direction of the reference layer.
15. A method of programming a magnetoresistive memory device, comprising:
providing the magnetoresistive memory device of claim 1 ; and
inducing the magnetic state transition in the electric field-modulated magnetic transition layer by applying a voltage between the first electrode and the second electrode to generate the external electric field.
16. The method of claim 15 , wherein:
the first electrode comprises a nonmagnetic metallic material;
the non-metallic magnetic material has a split conduction band in a ferromagnetic state; and
the electric field-modulated magnetic transition layer is configured to function as a tunnel barrier between the first electrode and the second electrode.
17. The method of claim 16 , wherein inducing the magnetic state transition comprises inducing a transition between a first state in which a magnetization direction in the lower split conduction band is parallel to a magnetization direction of the second electrode, and a second state in which the magnetization direction in the lower split conduction band is antiparallel to the magnetization of the second electrode.
18. The method of claim 17 , wherein:
the magnetoresistive memory device is in a lower resistance state when the magnetization direction in the lower split conduction band is parallel to a magnetization direction of the second electrode; and
the magnetoresistive memory device is in a higher resistance state when the magnetization direction in the lower split conduction band is antiparallel to a magnetization direction of the second electrode.
19. The method of claim 15 , wherein:
the first electrode comprises a ferromagnetic metallic material which has a lower coercivity than the ferromagnetic metallic material of the second electrode;
the non-metallic magnetic material has a split conduction band in a ferromagnetic state and also has a non-ferromagnetic state with the magnetic state transition between the ferromagnetic state and the non-ferromagnetic state that depends on the external electric field;
the electric field-modulated magnetic transition layer is configured to function as a tunnel barrier between the first electrode and the second electrode;
the magnetoresistive memory device has at least three different magnetoresistive memory states having a different resistance from each other;
the first electrode has a changeable magnetization direction and is configured to function as a free layer; and
the second electrode has a fixed magnetization direction and is configured to function as a reference layer.
20. The method of claim 19 , wherein inducing the magnetic state transition comprises inducing a transition between any two or more of:
a first magnetoresistive state in which the magnetization direction of the reference layer and the magnetization direction of the free layer are parallel to each other, and the electric field-modulated magnetic transition layer is in the ferromagnetic state in which the magnetization direction in a lower split conduction band is parallel to the magnetization direction of the reference layer;
a second magnetoresistive state in which the magnetization direction of the reference layer and the magnetization direction of the free layer are parallel to each other, and the electric field-modulated magnetic transition layer is in the non-ferromagnetic state;
a third magnetoresistive state in which the magnetization direction of the reference layer and the magnetization direction of the free layer are antiparallel to each other, and the electric field-modulated magnetic transition layer is in the ferromagnetic state in which the magnetization direction in the lower split conduction band is parallel to the magnetization direction of the reference layer;
a fourth magnetoresistive state in which the magnetization direction of the reference layer and the magnetization direction of the free layer are antiparallel to each other, and the electric field-modulated magnetic transition layer is in the non-ferromagnetic state; and
a fifth magnetoresistive state in which magnetization direction of the reference layer and the magnetization direction of the free layer are antiparallel to each other, and the electric field-modulated magnetic transition layer is in the ferromagnetic state in which the magnetization direction in the lower split conduction band is antiparallel to the magnetization direction of the reference layer.