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; and
a layer stack comprising an electric field-modulated magnetic transition layer and a ferroelectric insulator layer located between the first electrode and the second electrode, wherein 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;
wherein:
the non-metallic magnetic material is in the non-ferromagnetic state under a condition in which remanent polarization within the ferroelectric insulator layer points along a first direction toward, or away from, the electric field-modulated magnetic transition layer; and
the non-metallic magnetic material is in the ferromagnetic state under a condition in which the remanent polarization within the ferroelectric insulator layer points along a second direction that is antiparallel to the first direction.
2. The magnetoresistive memory device of claim 1 , wherein the non-metallic magnetic material comprises a semiconductor material or an insulator 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 2 , wherein:
the magnetoresistive memory device is in a lower resistance state when the non-metallic magnetic material is in the ferromagnetic state; and
the magnetoresistive memory device is in a higher resistance state when the non-metallic magnetic material is in the non-ferromagnetic state.
7. The magnetoresistive memory device of claim 6 , wherein:
the non-metallic magnetic material has a split conduction band in the ferromagnetic state; and
the non-ferromagnetic state comprises a paramagnetic state, a diamagnetic state, or an antiferromagnetic state.
8. The magnetoresistive memory device of claim 1 , wherein the non-metallic magnetic material comprises a doped transition metal oxide material.
9. 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.
10. The magnetoresistive memory device of claim 1 , wherein:
the electric field-modulated magnetic transition layer has a thickness in a range from 0.5 nm to 5 nm; and
the ferroelectric insulator layer has a thickness in a range from 0.5 nm to 5 nm.
11. The magnetoresistive memory device of claim 1 , wherein:
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.
12. The magnetoresistive memory device of claim 11 , wherein the ferroelectric insulator layer contacts the non-metallic magnetic material, such that the ferroelectric insulator layer is configured to hold the applied electric field after the voltage is switched off such that the state of the electric field-modulated magnetic transition layer is nonvolatile.
13. A method of programming a magnetoresistive memory device comprising a first electrode, a second electrode, and a layer stack comprising an electric field-modulated magnetic transition layer and a ferroelectric insulator layer located between the first electrode and the second electrode, wherein 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, the method comprising:
inducing a state transition between the ferromagnetic state and the non-ferromagnetic state 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;
wherein:
the first electrode is located adjacent to the electric field-modulated magnetic transition layer, such that the electric field-modulated magnetic transition layer is located between the ferroelectric insulator layer and the first electrode;
the second electrode is located adjacent to the ferroelectric insulator layer, such that the ferroelectric insulator layer is located between the electric field-modulated magnetic transition layer and the second electrode;
inducing the state transition in the electric field-modulated magnetic transition layer comprises changing the state of the non-metallic magnetic material of the electric field-modulated magnetic transition layer from the ferromagnetic state to the non-ferromagnetic state by applying a more positive voltage to the first electrode than to the second electrode;
inducing the state transition in the electric field-modulated magnetic transition layer further comprises changing the state of the non-metallic magnetic material of the electric field-modulated magnetic transition layer from the non-ferromagnetic state to the ferromagnetic state by applying a more negative voltage to the first electrode than to the second electrode;
the magnetoresistive memory device is in a lower resistance state when the non-metallic magnetic material is in the ferromagnetic state;
the magnetoresistive memory device is in a higher resistance state when the non-metallic magnetic material is in the non-ferromagnetic state;
the electric field-modulated magnetic transition layer functions as a tunnel barrier between the first electrode and the second electrode;
the non-ferromagnetic state comprises a paramagnetic state, a diamagnetic state, or an antiferromagnetic state; and
the non-metallic magnetic material has a split conduction band in the ferromagnetic state, wherein the lower conduction band has a lower energy than the conduction band in the paramagnetic state, such that the tunnel barrier height is lower in the ferromagnetic state than in the non-ferromagnetic state.
14. The method of claim 13 , further comprising determining a magnetic state of the electric field-modulated magnetic transition layer by measuring resistance between the first electrode and the second electrode.
15. A magnetoresistive memory device, comprising:
a first electrode;
a second electrode; and
a layer stack comprising an electric field-modulated magnetic transition layer and a ferroelectric insulator layer located between the first electrode and the second electrode, wherein 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;
wherein:
the non-metallic magnetic material comprises a semiconductor material or an insulator material;
the magnetoresistive memory device is in a lower resistance state when the non-metallic magnetic material is in the ferromagnetic state;
the magnetoresistive memory device is in a higher resistance state when the non-metallic magnetic material is in the non-ferromagnetic state;
the non-metallic magnetic material has a split conduction band in the ferromagnetic state; and
the non-ferromagnetic state comprises a paramagnetic state, a diamagnetic state, or an antiferromagnetic state.
16. The magnetoresistive memory device of claim 15 , wherein the non-metallic magnetic material comprises the semiconductor material.
17. The magnetoresistive memory device of claim 15 , wherein the non-metallic magnetic material comprises the insulator material.
18. A magnetoresistive memory device, comprising:
a first electrode;
a second electrode; and
a layer stack comprising an electric field-modulated magnetic transition layer and a ferroelectric insulator layer located between the first electrode and the second electrode, wherein 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;
wherein:
the external electric field is generated by applying a voltage between the first electrode and the second electrode;
the electric field-modulated magnetic transition layer is configured to function as a tunnel barrier between the first electrode and the second electrode; and
the ferroelectric insulator layer contacts the non-metallic magnetic material, such that the ferroelectric insulator layer is configured to hold the applied electric field after the voltage is switched off such that the state of the electric field-modulated magnetic transition layer is nonvolatile.