Magnetoresistive Element with Nonmagnetic Insertion Layer
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Solution Overview
Problem
Existing magnetoresistive elements with a three-layer structure face challenges in reducing read gap length and maintaining strong antiferromagnetic coupling due to crystal lattice mismatch at the interface between ferromagnetic layers and the spacer layer, which affects the strength of antiferromagnetic coupling and magnetoresistance change ratio.
Innovation Solution
Incorporating a nonmagnetic spacer layer and insertion layers with a face-centered cubic structure, where the spacer layer and insertion layers have atomic radii greater than the ferromagnetic material layers, to reduce lattice mismatch and enhance antiferromagnetic coupling between ferromagnetic layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a three-layer structure with ferromagnetic layers and spacer layer is used to reduce read gap length, then read gap length is reduced, but crystal lattice mismatch at the interface weakens antiferromagnetic coupling strength
Solution Approach 1:
The patent introduces a nonmagnetic insertion layer made of Ru, Rh, Ir, Re, Cr, Zr, or Cu between the ferromagnetic layer and the spacer layer. This insertion layer acts as an intermediary that mediates the interface between the two materials, reducing crystal lattice mismatch and maintaining strong antiferromagnetic coupling even when the read gap length is reduced to 30nm or less.
Solution Approach 2:
The patent changes the material parameters of the insertion layer by selecting elements with specific atomic radii (greater than Co and Fe) and face-centered cubic crystal structure. This parameter change optimizes the lattice constant matching between the ferromagnetic layer and spacer layer, thereby maintaining antiferromagnetic coupling strength while enabling reduced read gap length.
2Quantity of substance
If read gap length is reduced to increase recording density, then recording density is improved, but magnetoresistance change ratio deteriorates due to weakened antiferromagnetic coupling
Solution Approach 1:
The nonmagnetic insertion layer serves as a mediator that preserves the quality of the interface between the ferromagnetic layer and spacer layer. By reducing crystal lattice mismatch, it maintains the magnetoresistance change ratio even when the read gap length is reduced to enable higher recording density.
Solution Approach 2:
The patent creates a composite structure consisting of ferromagnetic layer + nonmagnetic insertion layer + spacer layer. This composite material structure combines the benefits of reduced read gap length with maintained antiferromagnetic coupling strength, thereby preserving magnetoresistance change ratio while increasing recording density.
3Length of stationary object
If spacer layer thickness is reduced to decrease read gap length, then read gap length is reduced, but interface quality deteriorates due to increased crystal lattice mismatch
Solution Approach 1:
The insertion layer acts as a buffer intermediary between the ferromagnetic layer and the thin spacer layer. It compensates for the increased stress and lattice mismatch that occur when the spacer layer is made very thin, thereby maintaining interface quality and reliability even at reduced read gap lengths.
Solution Approach 2:
The patent applies local quality improvement by introducing the insertion layer specifically at the critical interface region between the ferromagnetic layer and spacer layer. This localized intervention addresses the interface quality issue without affecting the overall spacer layer thickness, enabling maintained reliability with reduced read gap length.
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
This configuration allows for increased antiferromagnetic coupling strength and improved magnetoresistance change ratio, enabling a reduction in read gap length while maintaining stability and sensitivity in magnetoresistive elements.
Implementation Method 1
The technique of antiferromagnetically coupling the two ferromagnetic layers to each other by means of the RKKY interaction is utilized for a so-called synthetic pinned layer of a spin-valve GMR element.
Implementation Method 2
MR elements include GMR (giant magnetoresistive) elements utilizing a giant magnetoresistive effect
Implementation Method 3
TMR (tunneling magnetoresistive) elements utilizing a tunneling magnetoresistive effect
Data Source
AI summary
In an MR element, first and second ferromagnetic layers are antiferromagnetically coupled to each other through a spacer layer, and have magnetizations that are in opposite directions when no external magnetic field is applied thereto and that change directions in response to an external magnetic field. The spacer layer and the second ferromagnetic layer are stacked in this order on the first ferromagnetic layer. The first ferromagnetic layer includes a plurality of ferromagnetic material layers stacked, and an insertion layer made of a nonmagnetic material and inserted between respective two of the ferromagnetic material layers that are adjacent to each other along the direction in which the layers are stacked. The ferromagnetic material layers and the spacer layer each include a component whose crystal structure is a face-centered cubic structure. The spacer layer and the insertion layer are each composed of an element having an atomic radius greater than that of at least one element constituting the ferromagnetic material layers.