Magnetoresistive Memory Write Circuit Using Constant Current

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Solution Overview

Problem

The magnetization reversal period in magnetoresistive effect memory is very short, making pulse control difficult.

Innovation Solution

A magnetoresistive effect memory that includes a magnetoresistive element with a fixed layer and a recording layer, and a write circuit that reverses the magnetization of the recording layer by applying a current limited to a predetermined magnitude, allowing the resistance value of the magnetoresistive element to switch between low and high resistance values.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If voltage pulse is applied to reverse magnetization in MITJ element, then magnetization reversal is achieved, but pulse control becomes difficult due to very short magnetization reversal period

Engineering Contradiction:

Improvemagnetization reversal speedVSAvoidpulse control difficulty

Core Design Contradiction:

SpeedVSEase of operation

Solution Approach 1:

The patent replaces voltage control (electrical field) with current control (electrical current) for magnetization reversal. By using a constant current source instead of voltage pulses, the system exploits the gradual resistance change during magnetization rotation to achieve reliable reversal without requiring precise timing control, thus substituting the voltage-based mechanism with a current-based mechanism that is easier to control.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent utilizes the resistance value of the magnetoresistive element as feedback during the magnetization reversal process. The constant current source maintains current flow while the resistance gradually changes as magnetization rotates, allowing the system to naturally complete the reversal process without external timing intervention, effectively using the element's own resistance change as a feedback signal.

Inventive Principle:

Principle #23Feedback

2Reliability

If voltage pulse timing is precisely controlled to achieve magnetization reversal, then reversal success rate improves, but circuit complexity increases

Engineering Contradiction:

Improvemagnetization reversal success probabilityVSAvoidcircuit complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces complex voltage pulse timing control circuits with a simple constant current source. This substitution eliminates the need for precise timing synchronization circuits while maintaining high reversal success probability, as the constant current naturally adapts to the resistance changes during magnetization rotation without requiring external timing control.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The magnetoresistive element itself provides the control mechanism through its resistance change during magnetization rotation. The constant current source simply needs to be applied, and the element's own resistance variation during the reversal process automatically regulates the current effect, making the element self-controlling and eliminating the need for external complex control circuits.

Inventive Principle:

Principle #25Self-service

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

Facilitates pulse control for reversing magnetization, reducing the need for highly accurate pulse control and improving the success probability of magnetization reversal, while also simplifying circuit design.

Implementation Method 1

the magnetization of the recording layer rotates by precession around a magnetic field in a plane direction of the layer when a voltage is applied to the magnetoresistive element

Methodology Applied

Scientific EffectPrecession: Precession

Implementation Method 2

a magnetoresistive element including a fixed layer whose magnetization direction is fixed and a recording layer whose magnetization direction changes

Methodology Applied

Scientific EffectMagnetoresistive effect: Magnetoresistance

Data Source

PatentUS20250140297A1Magnetoresistive effect memory

Publication Date: 2025.05.01 SONY SEMICON SOLUTIONS CORP

AI summary

A magnetoresistive effect memory (100) includes: a magnetoresistive element (11) including a fixed layer (111) whose magnetization direction is fixed and a recording layer (113) whose magnetization direction changes; and a write circuit (24) that reverses magnetization of the recording layer (113) so that a resistance value of the magnetoresistive element (11) is switched between a low resistance value and a high resistance value, in which the magnetization of the recording layer (113) rotates by precession around a magnetic field in a plane direction of the layer when a voltage is applied to the magnetoresistive element (11), the resistance value of the magnetoresistive element (11) gradually changes between the low resistance value and the high resistance value during the rotation of the magnetization of the recording layer (113), and the write circuit (24) reverses the magnetization of the recording layer (113) so that the resistance value of the magnetoresistive element (11) is switched from the high resistance value to the low resistance value by applying a current limited so as to have a predetermined magnitude to the magnetoresistive element (11).