Magnetic Oscillation Element MgO Tunnel Barrier
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Solution Overview
Problem
High-density magnetic recording faces limitations due to increased noise components, particularly shot noise and magnetic white noise, which hinder further miniaturization and signal purity in TMR elements, and signal delay issues in highly integrated LSIs necessitate the development of alternative magnetic oscillation elements.
Innovation Solution
A magnetic oscillation element with a magnetization fixing layer, nonmagnetic layers, and magnetization free layers excited by spin transfer, utilizing materials with perpendicular magnetization and artificial ferrimagnetic substances to reduce thermal noise and magnetic field dependency, thereby narrowing the oscillation line width and enhancing signal purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the tunnel insulating layer is thinned to reduce tunnel resistance and suppress shot noise, then the signal voltage increases, but short circuit between electrodes occurs more easily and manufacturing becomes dramatically difficult
Solution Approach 1:
The patent changes the material parameter of the insulating layer from conventional Al-O to Mg-O (magnesium oxide), which has different electrical and structural properties. This material substitution allows achieving low tunnel resistance with a thicker insulating layer, thereby avoiding short circuits while maintaining signal voltage levels.
Solution Approach 2:
The patent employs a composite structure combining Mg-O insulating layer with specific ferromagnetic layer configurations. This composite approach enables optimized tunnel characteristics without requiring extreme thinning of the insulating layer, thus resolving the contradiction between signal quality and manufacturability.
2Quantity of substance
If the element size is reduced to match record bit size for higher density, then recording density increases, but thermal noise and magnetic white noise become more dominant
Solution Approach 1:
The patent modifies the insulating layer material parameter to Mg-O, which provides superior electrical insulation properties. This allows maintaining adequate insulation thickness even in miniaturized elements, thereby suppressing thermal noise and magnetic white noise while achieving high recording density.
3Quantity of substance
If the insulating layer is thinned to achieve joint resistance of 1Ω·cm2 or less for 300 gigabits/inch2 density, then recording density increases, but short circuit occurs more easily and element fabrication becomes dramatically difficult
Solution Approach 1:
The patent substitutes the insulating layer material from Al-O to Mg-O, changing the fundamental material parameter. Magnesium oxide provides higher breakdown voltage and better insulation properties, enabling achievement of 1Ω·cm2 joint resistance with a thicker, more reliable insulating layer that resists short circuits.
4Power
If TMR element is used to achieve larger MR ratio and signal voltage, then signal voltage increases, but shot noise increases proportionally to square root of tunnel resistance
Solution Approach 1:
The patent changes the insulating layer material parameter to Mg-O, which enables optimized tunnel barrier characteristics. This material substitution allows achieving the necessary signal voltage with controlled tunnel resistance, thereby maintaining acceptable shot noise levels while preserving the high MR ratio advantage of TMR elements.
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
The solution effectively reduces thermal noise and magnetic field dependency, achieving higher signal purity and potentially increasing recording density beyond 300 gigabits/inch² while addressing signal delay issues in LSIs through the use of magnetic oscillation elements.
Implementation Method 1
the magnetization free layer is excited with a magnetization oscillation caused by spin transfer from the magnetization fixing layer due to the appliance of the current
Implementation Method 2
applying an exchange bias to one ferromagnetic layer for fixing magnetization thereof
Implementation Method 3
using the magneto-resistance effect of a spin valve film for applying an exchange bias to one ferromagnetic layer for fixing magnetization thereof and changing the magnetization direction of the other ferromagnetic layer by an external magnetic field for detecting change in the relative angle of the magnetization directions of the two ferromagnetic layers as change in the resistance value
Implementation Method 4
The TMR element includes stacked films of tunnel insulating layer made up of ferromagnetic layer/insulator/ferromagnetic layer, and a voltage is applied to the nip between the ferromagnetic layers for allowing a tunnel current to flow. The TMR element is an element for using the fact that the magnitude of the tunnel current changes depending on the direction of magnetization of the top and bottom ferromagnetic layers and detecting change in the relative angle of magnetization as change in the tunnel resistance value
Data Source
AI summary
A magnetic oscillation element includes a magnetization fixing layer whose magnetization direction is substantially pinned toward one direction, a nonmagnetic layer that is disposed on the magnetization fixing layer, and a magnetization free layer whose magnetization direction fluctuates. The magnetization free layer is disposed on the nonmagnetic layer. A pair of electrodes apply a current in a direction perpendicular to the film surface of the magnetization fixing layer, the nonmagnetic layer, and the magnetization free layer. The magnetization free layer is excited with a magnetization vibration caused by spin transfer from the magnetization fixing layer due to the appliance of the current.