Racetrack Memory Domain Wall Injection via Electric Field Anisotropy

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Solution Overview

Problem

Magnetic shift register memories require high current densities for injecting domain walls, leading to significant power dissipation.

Innovation Solution

A method involving a magnetic racetrack memory with a nanowire coupled to a gate and a pinning layer, utilizing surface anisotropy modulation via an electric field and spin torque or Oersted field to inject domain walls, minimizing power dissipation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If domain wall injection is performed using local magnetic field or current-induced spin-torque switching, then domain wall injection is achieved, but large current densities are required leading to high power dissipation

Engineering Contradiction:

Improvedomain wall injectionVSAvoidpower dissipation

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent changes the physical parameter used for domain wall injection from magnetic field or spin-torque (requiring large currents) to electric field control of surface anisotropy. By applying an electric field to modulate the surface anisotropy energy at the ferromagnetic/dielectric interface, the system achieves domain wall injection at significantly lower current densities, directly resolving the power dissipation problem.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent substitutes the mechanical/electrical system (current-induced spin torque) with an electric field system. Instead of using spin-polarized electrons to exert torque on the magnetization, the invention uses electric field-induced surface anisotropy modulation, replacing a complex spin transport mechanism with a more efficient electric field control mechanism.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If high current densities are used for domain wall injection, then domain wall injection is achieved, but write operation power consumption increases

Engineering Contradiction:

Improvewrite operationVSAvoidwrite power consumption

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The patent changes the control parameter for write operations from current density to electric field strength. By modulating the surface anisotropy energy through electric field application, the system achieves domain wall injection with minimal current flow, directly reducing write power consumption while maintaining reliable write operations.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces surface anisotropy energy as an intermediary mechanism between the electric field and domain wall motion. The electric field does not directly move the domain wall but instead modulates the surface anisotropy energy at the interface, which then facilitates domain wall injection. This intermediary mechanism enables low-power control.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If conventional domain wall injection methods are used, then magnetization switching is achieved, but the write coercive field threshold is high

Engineering Contradiction:

Improvemagnetization switchingVSAvoidwrite coercive field threshold

Core Design Contradiction:

ReliabilityVSForce

Solution Approach 1:

The patent changes the energy landscape by dynamically modulating the surface anisotropy energy through electric field application. By reducing the surface anisotropy energy barrier at the ferromagnetic/dielectric interface, the system lowers the write coercive field threshold required for magnetization switching, enabling easier domain wall injection while maintaining reliable switching.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Reduces power dissipation by controlling domain wall injection through electrical means, lowering the write coercive field threshold and critical current, while maintaining efficient magnetization direction establishment.

Implementation Method 1

The injection of the domain wall may be based on an electrical control of surface anisotropy at one or more ferromagnetic metal/dielectric interfaces

Methodology Applied

Scientific EffectSurface anisotropy: Anisotropy

Implementation Method 2

local anisotropy in a nanowire may be modulated via an electric field

Methodology Applied

Scientific EffectElectric field: Electric Field

Implementation Method 3

at least one antiferromagnet configured to induce an exchange bias locally on the nanowire

Methodology Applied

Scientific EffectExchange bias:

Implementation Method 4

spin torque or Oersted field to inject domain walls

Methodology Applied

Scientific EffectSpin torque:

Implementation Method 5

spin torque or Oersted field to inject domain walls

Methodology Applied

Scientific EffectOersted field: Electromagnetic Induction

Data Source

PatentUS9042151B2Racetrack memory with electric-field assisted domain wall injection for low-power write operation

Publication Date: 2015.05.26 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

Embodiments are directed to injecting domain walls in a magnetic racetrack memory. In some embodiments, a racetrack comprising a nanowire is coupled with a gate in order to manipulate an anisotropy associated with the nanowire. The racetrack and gate is coupled with a pinning layer configured to establish a magnetization direction in the nanowire.