Circuits and devices based on enhanced spin Hall effect for efficient spin transfer torque

Patent metadata

Field	Value
Publication number	US-10847197-B2
Application number	US-201816017565-A
Country	US
Kind code	B2
Filing date	Jun 25, 2018
Priority date	Jul 17, 2014
Publication date	Nov 24, 2020
Grant date	Nov 24, 2020

Abstract

Devices or circuits based on spin torque transfer (STT) and Spin Hall effect are disclosed by using a spin Hall effect (SHE) metal layer coupled to a magnetic free layer for various applications. The efficiency or strength of the STT effect based on this combination of SHE and STT can be enhanced by an interface modification between the SHE metal layer and the magnetic free layer or by modifying or engineering the SHE metal layer by doping the SHE metal with certain impurities or other means.

First claim

What is claimed is what is described and illustrated, including:

1. A magnetic tunneling junction memory device based on a two-terminal circuit configuration and based on a spin Hall effect (SHE) and spin transfer torque (STT) effect, comprising:
an array of memory cells for storing data; and
a memory control circuit coupled to the array of memory cells and operable to read or write data in the memory cells,
wherein each memory cell includes a magnetic tunneling junction (MTJ) which includes (1) a free magnetic layer having a magnetization direction that can be changed by spin transfer torque, (2) a pinned magnetic layer having a fixed magnetization direction and (3) a non-magnetic junction layer between the free magnetic layer and the pinned magnetic layer to allow tunneling of electrons between the free magnetic layer and the pinned magnetic layer and further includes:
a spin Hall effect metal layer below the MTJ and responsive to a charge current in the spin Hall effect metal layer to generate a spin-polarized current that is due to a spin Hall effect (SHE) in a material of the spin Hall effect metal layer and is perpendicular to the charge current;
a thin high-resistivity metal insertion layer in contact with and between the spin Hall effect metal layer and the free magnetic layer of the MTJ, wherein the thin high-resistivity metal insertion layer is structured to include an insertion material (1) that is different from the material of the spin Hall effect metal layer for generating the spin-polarized current and (2) that exhibits a resistivity higher than a resistivity of the spin Hall effect metal layer;
a first electrical terminal in electrical contact with the MTJ from a side having the pinned magnetic layer to receive a gate voltage that modifies a current threshold of a spin-polarized current flowing across the MTJ for switching the magnetization of the free magnetic layer; and
a second electrical terminal in electrical contact with a contact location of the spin Hall effect metal layer,

wherein the thin high-resistivity metal insertion layer includes a non-magnetic metal layer having a thickness of at least one atomic layer thick but no thicker than the spin diffusion length.

2. A magnetic tunneling junction memory device based on a two-terminal circuit configuration and based on a spin Hall effect (SHE) and spin transfer torque (STT) effect, comprising:
an array of memory cells for storing data; and
a memory control circuit coupled to the array of memory cells and operable to read or write data in the memory cells,
wherein each memory cell includes a magnetic tunneling junction (MTJ) which includes (1) a free magnetic layer having a magnetization direction that can be changed by spin transfer torque, (2) a pinned magnetic layer having a fixed magnetization direction and (3) a non-magnetic junction layer between the free magnetic layer and the pinned magnetic layer to allow tunneling of electrons between the free magnetic layer and the pinned magnetic layer and further includes:
a spin Hall effect metal layer below the MTJ and responsive to a charge current in the spin Hall effect metal layer to generate a spin-polarized current that is due to a spin Hall effect (SHE) in a material of the spin Hall effect metal layer and is perpendicular to the charge current;
a thin high-resistivity metal insertion layer in contact with and between the spin Hall effect metal layer and the free magnetic layer of the MTJ, wherein the thin high-resistivity metal insertion layer is structured to include an insertion material (1) that is different from the material of the spin Hall effect metal layer for generating the spin-polarized current and (2) that exhibits a resistivity higher than a resistivity of the spin Hall effect metal layer;
a first electrical terminal in electrical contact with the MTJ from a side having the pinned magnetic layer to receive a gate voltage that modifies a current threshold of a spin-polarized current flowing across the MTJ for switching the magnetization of the free magnetic layer; and
a second electrical terminal in electrical contact with a contact location of the spin Hall effect metal layer,

wherein an interface of the thin high-resistivity metal insertion layer with the free magnetic layer has a spin mixing conductance that is greater than the conductance of the insertion layer itself.

3. A magnetic tunneling junction memory device based on a two-terminal circuit configuration and based on a spin Hall effect (SHE) and spin transfer torque (STT) effect, comprising:
an array of memory cells for storing data; and
a memory control circuit coupled to the array of memory cells and operable to read or write data in the memory cells,
wherein each memory cell includes a magnetic tunneling junction (MTJ) which includes (1) a free magnetic layer having a magnetization direction that can be changed by spin transfer torque, (2) a pinned magnetic layer having a fixed magnetization direction and (3) a non-magnetic junction layer between the free magnetic layer and the pinned magnetic layer to allow tunneling of electrons between the free magnetic layer and the pinned magnetic layer and further includes:
a spin Hall effect metal layer below the MTJ and responsive to a charge current in the spin Hall effect metal layer to generate a spin-polarized current that is due to a spin Hall effect (SHE) in a material of the spin Hall effect metal layer and is perpendicular to the charge current;
a thin high-resistivity metal insertion layer in contact with and between the spin Hall effect metal layer and the free magnetic layer of the MTJ, wherein the thin high-resistivity metal insertion layer is structured to include an insertion material (1) that is different from the material of the spin Hall effect metal layer for generating the spin-polarized current and (2) that exhibits a resistivity higher than a resistivity of the spin Hall effect metal layer;
a first electrical terminal in electrical contact with the MTJ from a side having the pinned magnetic layer to receive a gate voltage that modifies a current threshold of a spin-polarized current flowing across the MTJ for switching the magnetization of the free magnetic layer; and
a second electrical terminal in electrical contact with a contact location of the spin Hall effect metal layer,

wherein the thin high-resistivity metal insertion layer is configured to exhibit an electrical resistivity of about two times or more greater than an electrical resistivity of the spin Hall effect base layer.

4. The device as in claim 1 , wherein the spin Hall metal layer includes Pt, Pd, Ta, W, Hf, Nb, Mo, Ru, Re, Os, Ir, Au, Tl, Pb, Bi, one or more alloys based upon Pt, Pd, Ta, W, Hf, Nb, Mo, Ru, Re, Os, Ir, Au, Tl, Pb, Bi, Cu1-x Bi x, Ag1-xBix, Cu1-xIrx, Ag1-xIrx, Cu1-xWx, Ag1-xWx, Cu1-xTax, Ag1-xTax, or HfxIry.

5. The device as in claim 1 , wherein the spin Hall metal layer includes a composite structure that includes Pt.

6. A device based on a spin Hall effect (SHE) and spin transfer torque (STT) effect, comprising:
a magnetic structure including a ferromagnetic layer having a magnetization direction that can be changed by spin transfer torque;
a spin Hall effect metal layer below the magnetic structure and responsive to a charge current in the spin Hall effect metal layer to generate a spin-polarized current that is perpendicular to the charge current;
a thin high-resistivity metal insertion layer in contact with and between the spin Hall effect metal layer and the free magnetic layer of the MTJ;
a first electrical contact in contact with a first location of the SHE layer;
a second electrical contact in contact with a second location of the SHE layer so that the first and second locations are on two opposite sides of the magnetic

Assignees

• Univ Cornell

Inventors

• Buhrman Robert A
• Nguyen Minh-Hai
• Pai Chi-Feng
• Ralph Daniel C

Classifications

• H10D48/385

  Devices using spin-polarised carriers · CPC title

• H10N50/85

  Materials of the active region · CPC title

• G11C11/18

  using Hall-effect devices · CPC title

• G11C11/1675

  Writing or programming circuits or methods · CPC title

• G11C11/1673

  Reading or sensing circuits or methods · CPC title