Magnetic device including multiferroic regions and methods of forming the same

Patent metadata

Field	Value
Publication number	US-11222920-B2
Application number	US-202016781225-A
Country	US
Kind code	B2
Filing date	Feb 4, 2020
Priority date	Feb 4, 2020
Publication date	Jan 11, 2022
Grant date	Jan 11, 2022

Abstract

A magnetic device includes a first electrode, a second electrode, a plurality of magnetic junctions each containing a ferromagnetic reference layer and a ferromagnetic free layer located between the first electrode and the second electrode, and a plurality of magnetoelectric multiferroic portions having different structural defect densities located between the first electrode and the second electrode. Each of the plurality of magnetoelectric multiferroic portions is magnetically coupled to the ferromagnetic free layer of a respective one of the plurality of magnetic junctions.

First claim

What is claimed is:

1. A magnetic device, comprising:
a first electrode;
a second electrode;
a plurality of magnetic junctions each comprising a ferromagnetic reference layer and a ferromagnetic free layer located between the first electrode and the second electrode;
a plurality of magnetoelectric multiferroic portions having different structural defect densities located between the first electrode and the second electrode, wherein each of the plurality of magnetoelectric multiferroic portions is magnetically coupled to the ferromagnetic free layer of a respective one of the plurality of magnetic junctions; and
further comprising at least one feature selected from:
(a) a first feature in which:
the different structural defect densities comprise a different density of broken bonds in the different magnetoelectric multiferroic portions; or

(b) a second feature in which:
the different structural defect densities comprise a different density of displaced atoms in a crystal lattice in the different magnetoelectric multiferroic portions; or

(c) a third feature in which:
the different structural defect densities comprise a different density of gallium or helium atoms in the different magnetoelectric multiferroic portions; or

(d) a fourth feature in which:
the plurality of magnetoelectric multiferroic portions comprise a first magnetoelectric multiferroic portion having a first structural defect density and a first ferroelectric coercivity; and a second magnetoelectric multiferroic portion having a second structural defect density higher than the first structural defect density, and a second ferroelectric coercivity higher than the first ferroelectric coercivity; or

(e) a fifth feature in which:
the plurality of magnetoelectric multiferroic portions comprise portions without distinct boundaries within a single continuous magnetoelectric multiferroic layer having a graded structural defect density that monotonically laterally changes from one side to another; and the plurality of magnetic junctions comprise a continuous polycrystalline ferromagnetic free layer having a plurality of grains separated by domain wall grain boundaries.

2. The magnetic device of claim 1 , wherein the magnetic device comprises a magnetoresistive memory device, and the plurality of magnetic junctions comprise a plurality of magnetic tunnel junctions each comprising a tunnel barrier layer.

3. The magnetic device of claim 2 , wherein the plurality of magnetoelectric multiferroic portions comprise a material selected from BiFeO 3 , h-YMnO 3 , BaNiF 4 , PbVO 3 , BiMnO 3 , LuFe 2 O 4 , HoMn 2 O 5 , h-HoMnO 3 , h-ScMnO 3 , h-ErMnO 3 , h-TmMnO 3 , h-YbMnO 3 , h-LuMnO 3 , K 2 SeO 4 , Cs 2 CdI 4 , TbMnO 3 , Ni 3 V 2 O 8 , MnWO 4 , CuO, ZnCr 2 Se 4 , LiCu 2 O 2 , or Ni 3 B 7 O 13 I.

4. The magnetic device of claim 3 , wherein the plurality of magnetoelectric multiferroic portions comprise BiFeO 3 .

5. A magnetic device, comprising:
a first electrode;
a second electrode;
a plurality of magnetic junctions each comprising a ferromagnetic reference layer and a ferromagnetic free layer located between the first electrode and the second electrode; and
a plurality of magnetoelectric multiferroic portions having different structural defect densities located between the first electrode and the second electrode, wherein each of the plurality of magnetoelectric multiferroic portions is magnetically coupled to the ferromagnetic free layer of a respective one of the plurality of magnetic junctions;
wherein:
each of the plurality of magnetoelectric multiferroic portions has a respective canted magnetic moment direction and a respective ferroelectric polarization direction; and
a relative spatial orientation between the respective canted magnetic moment direction and a respective ferroelectric polarization direction within each magnetoelectric multiferroic portion is the same.

6. The magnetic device of claim 5 , wherein each magnetoelectric multiferroic portion contacts a respective ferromagnetic free layer, and has a respective out of plane component of the canted magnetic moment direction that is magnetically coupled to the respective free layer via exchange coupling or bias.

7. The magnetic device of claim 6 , wherein magnetoresistance between the first electrode and the second electrode has at least three different values that depend on the respective canted magnetic moment direction of the plurality of magnetoelectric multiferroic portions and the magnetization direction of the respective magnetically coupled free layer relative to the magnetization direction of the reference layer in the same magnetic junction.

8. The magnetic device of claim 1 , wherein:
the first electrode comprises a bottom electrode;
the second electrode comprises a top electrode located over the bottom electrode; and
the plurality of magnetic junctions are located above or below the plurality of magnetoelectric multiferroic portions.

9. The magnetic device of claim 1 , wherein the at least one feature comprises the first feature.

10. The magnetic device of claim 1 , wherein the at least one feature comprises the second feature.

11. The magnetic device of claim 1 , wherein the at least one feature comprises the third feature.

12. The magnetic device of claim 1 , wherein the at least one feature comprises the fourth feature.

13. The magnetic device of claim 1 , wherein the plurality of magnetic junctions comprise discrete magnetic tunnel junctions that do not directly contact one another, and wherein the plurality of magnetoelectric multiferroic portions are separated by distinct boundaries.

14. The magnetic device of claim 1 , wherein the at least one feature comprises the fifth feature.

15. An interconnected network of magnetic devices that are connected in a synaptic connection configuration, wherein the magnetic devices comprise:
a first electrode;
a second electrode;
a plurality of magnetic junctions each comprising a ferromagnetic reference layer and a ferromagnetic free layer located between the first electrode and the second electrode; and
a plurality of magnetoelectric multiferroic portions having different structural defect densities located between the first electrode and the second electrode, wherein each of the plurality of magnetoelectric multiferroic portions is magnetically coupled to the ferromagnetic free layer of a respective one of the plurality of magnetic junctions.

16. A method of forming a magnetic device, comprising:
forming a bottom electrode;
forming a continuous magnetoelectric multiferroic layer over the bottom electrode;
forming a plurality of magnetoelectric multiferroic portions in the continuous magnetoelectric multiferroic layer by structurally damaging different portions of the continuous magnetoelectric multiferroic layer with different structural defect densities;
forming a plurality of magnetic junctions located over or under the plurality of magnetoelectric multiferroic portions, wherein each of the magnetic junctions comprises a respective reference layer and a respective free layer contacting a respective one of the magnetoelectric multiferroic portions; and
forming a top electrode over the bottom electrode, the plurality of magnetoelectric multiferroic portions and the plurality of magnetic junctions.

17. The method of claim 16 , wherein structurally damaging different portions of the continuous magnetoelectric multiferroic layer comprises performing a different focused ion beam irradiation process in each of the plurality of magnetoelectric multiferroic portions to provid

Assignees

• Western Digital Tech Inc

Inventors

• Prasad Bhagwati
• Kalitsov Alan

Classifications

• H10N50/85

  Materials of the active region · CPC title

• G11C11/5607

  using magnetic storage elements · CPC title

• H01F10/3272

  by use of anti-parallel coupled [APC] ferromagnetic layers, e.g. artificial ferrimagnets [AFI], artificial [AAF] or synthetic [SAF] anti-ferromagnets · CPC title

• G06N10/40

  Physical realisations or architectures of quantum processors or components for manipulating qubits, e.g. qubit coupling or qubit control · CPC title

• G06N3/04

  Architecture, e.g. interconnection topology · CPC title