RuCu Alloy Pinned Layer for GMR Stability
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Solution Overview
Problem
The synthetic CPP-GMR element with a synthetic antiferromagnetic pinned layer experiences resistance change cancellation due to opposing magnetization directions, leading to reduced net moment and stability issues, which hinders higher recording density and magnetic field stability.
Innovation Solution
A magnetoresistive device with a synthetic antiferromagnetic pinned layer using a ruthenium copper alloy as the nonmagnetic intermediate layer, allowing thicker magnetization pinned layers to be antiferromagnetically coupled over a wider magnetic field range, increasing resistance change and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a synthetic antiferromagnetic pinned layer with two ferromagnetic layers having anti-parallel magnetization directions is used, then magnetic field stability and suppression of magnetization rotation are improved, but resistance change amount decreases due to cancellation effect
Solution Approach 1:
The patent applies local quality by creating an asymmetric structure where the first ferromagnetic layer has different thickness and magnetization characteristics than the second ferromagnetic layer. Specifically, the first layer is designed with thinner thickness and lower magnetization saturation to contribute less to the net moment, while the second layer has greater thickness and higher magnetization saturation to dominate the resistance change response. This local differentiation in layer properties resolves the contradiction by maintaining the stabilizing anti-parallel coupling while ensuring the dominant layer provides sufficient resistance change signal.
Solution Approach 2:
The patent employs composite materials by combining multiple ferromagnetic layers with distinct magnetic properties (different thicknesses, saturation magnetizations, and coercive fields) with a nonmagnetic intermediate layer. This composite structure allows the first layer to provide magnetic field stability through anti-parallel coupling while the second layer, having superior magnetic moment characteristics, dominates the resistance change response. The composite nature of the pinned layer enables simultaneous achievement of stability and measurement precision.
2Quantity of substance
If the dimension in the read track width direction is reduced to increase recording density, then recording capacity improves, but output voltage decreases in CIP-GMR elements due to smaller magnetosensitive area
Solution Approach 1:
The patent applies dimensionality change by transitioning from CIP-GMR (current in-plane) to CPP-GMR (current perpendicular-to-plane) geometry. In CPP-GMR, the read current flows vertically through the magnetoresistive stack rather than horizontally along the plane, effectively utilizing the stacking direction as the current path dimension. This geometric transformation allows the magnetosensitive area to remain effective even when the lateral track width is reduced, thereby maintaining output voltage while enabling higher recording density through narrower tracks.
3Reliability
If ruthenium only is used as the nonmagnetic intermediate layer, then exchange coupling strength is sufficient, but resistance value and spin scattering length are suboptimal for high-density applications
Solution Approach 1:
The patent employs composite materials by replacing pure ruthenium with a ruthenium-copper alloy for the nonmagnetic intermediate layer. This alloy composition provides optimized electrical resistance and spin scattering length characteristics compared to pure ruthenium, while maintaining adequate exchange coupling strength between the ferromagnetic layers. The composite alloy structure enables improved resistance change amount and enhanced spin-dependent scattering effects necessary for high-density magnetic recording applications.
Solution Approach 2:
The patent applies parameter changes by modifying the composition of the nonmagnetic intermediate layer from pure ruthenium to a ruthenium-copper alloy with specific atomic percentages (e.g., Ru80Cu20, Ru70Cu30, Ru60Cu40). This compositional parameter change optimizes the electrical resistance, spin scattering length, and exchange coupling characteristics of the intermediate layer, enabling improved magnetoresistive effect and signal detection capability for high-density recording.
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 use of a ruthenium copper alloy in the nonmagnetic intermediate layer enhances resistance change and magnetic field stability, enabling higher recording density and precise current measurement in magnetic memory cells and sensors.
Implementation Method 1
exchange coupling occurs between the two ferromagnetic layers, so that the magnetization directions are stabilized
Implementation Method 2
a synthetic antiferromagnetic pinned layer having a pair of ferromagnetic layers which are antiferromagnetic-coupled to each other with a nonmagnetic intermediate layer in between
Implementation Method 3
a thin film magnetic head using a giant magneto-resistive device (GMR device) exhibiting the GMR effect
Implementation Method 4
electric resistance (that is, voltage) changes when sense current is passed according to relative angles of the magnetization directions in the two magnetic layers
Data Source
AI summary
An MR device includes a magnetization pinned film having a nonmagnetic intermediate layer positioned on the opposite side of a magnetization free layer while sandwiching a nonmagnetic spacer layer and made of RuCu. In the case of passing read current in the stacking direction via lower and upper electrodes, decrease in a resistance change amount caused by a second magnetization pinned layer can be suppressed. Further, a first magnetization pinned layer and the second magnetization pined layer which are thicker can be antiferromagnetically coupled to each other in magnetic fields in a wider range. Thus, both increase in the resistance change amount and magnetic field stability can be achieved. Therefore, while maintaining stable operations by reducing the influence of external noise, the invention can address higher recording density by the increase in the resistance change amount as a whole.