Spin-orbit torque magnetoresistive random access memory with magnetic field-free current-induced perpendicular magnetization reversal
AssigneeWisconsin Alumni Research Foundation
InventorsJiamian Hu, Minyi Dai
Life of this patent
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Abstract
Spin-orbit torque magnetoresistive random-access memory (SOT-MRAM) cells that undergo perpendicular magnetization switching in the absence of an in-plane magnetic field and methods for their operation are provided. The SOT-MRAM cells use cobalt-iron-boron alloys, cobalt-iron alloys, metallic cobalt, and/or metallic iron as the ferromagnetic free layer in a magnetic tunnel junction. By designing the ferromagnetic layer with appropriate lateral dimensions and operating the SOT-MRAM cells with an appropriate charge current density, deterministic perpendicular magnetization switching is achieved without the need to apply an external in-plane bias collinear with the charge current.
Claims25
A field free method of deterministically switching a spin-orbit torque magnetoresistive random-access memory cell, the memory cell comprising:
- a structurally symmetric circular magnetic tunnel junction comprising:
- a free layer comprising CoFeB, CoFe, metallic cobalt, or metallic iron and having a perpendicular direction of magnetization;
- a pinned layer comprising a ferromagnetic material having a fixed perpendicular direction of magnetization;
- and
- a barrier layer comprising an electrically insulating material separating the free layer from the pinned layer;
- a structurally symmetric spin current layer comprising a non-magnetic material in contact with the free layer at an interface, wherein the spin current layer is not interfaced with a strain-inducing layer;
- and
- a write line in electrical communication with the spin current layer;
- and
- a read line in electrical communication with the magnetic tunnel junction,
- the method comprising:
- passing an in-plane write current through the spin current layer in the absence of a colinear in-plane magnetic field, whereby an out-of-plane spin current running parallel with the direction of magnetization of the free layer is generated in the spin current layer, giving rise to a spin torque in the free layer that deterministically fully reverses the perpendicular direction of magnetization of the free layer, wherein the reversal of the perpendicular direction of magnetization is not strain-mediated;
- and
- passing a read current through the magnetic tunnel junction and measuring the resistance of the magnetic tunnel junction.
A spin-orbit torque magnetic random-access memory cell comprising:
- a structurally symmetric circular magnetic tunnel junction comprising:
- a free layer comprising CoFeB, CoFe, metallic cobalt, or metallic iron and having a perpendicular magnetic anisotropy, the free layer having a diameter in the size range from 35 nm to 80 nm;
- a pinned layer comprising a ferromagnetic material having a fixed perpendicular direction of magnetization;
- and
- a barrier layer comprising an electrically insulating material separating the free layer from the pinned layer;
- and
- a structurally symmetric spin current layer comprising a non-magnetic material in contact with the free layer at an interface, wherein the Dyzaloshinskii-Moriya interaction at the interface is in the range from 0.2 mJ/m2 to 3.2 mJ/m2.
Dependencies are inferred from the claim text.