CPP-GMR Free Layer Ternary Alloy for High MR Ratio
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Solution Overview
Problem
CPP-GMR elements face challenges in achieving a large magneto-resistance ratio without increasing the thickness of the SV film, which is limited, and require soft magnetic properties for effective magnetic head performance.
Innovation Solution
A CPP-GMR element with a thin SV film structure, featuring a free layer composed of a nonmagnetic copper layer and ternary alloy layers containing cobalt, iron, and nickel, with specific atomic percentage ratios and thicknesses, to enhance magneto-resistance ratio while maintaining soft magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the thickness of the free layer and pinned layer is increased to achieve a large magneto-resistance ratio in CPP-GMR elements, then the magneto-resistance ratio is improved, but the total film thickness increases which is not preferable for high linear recording density
Solution Approach 1:
The invention changes the material composition parameters of the free layer by introducing a ternary alloy layer with specific ratios of Co, Fe, and Ni (where the ratio of Ni to total Ni and Fe is 27-45%). This compositional parameter change enables achieving high magneto-resistance ratio with reduced film thickness by optimizing the spin scattering properties at the Cu interface without increasing the overall layer thickness
Solution Approach 2:
The invention uses a composite structure in the free layer consisting of a Cu nonmagnetic layer combined with a ternary alloy layer (Co-Fe-Ni). This composite material approach leverages the high spin scattering capability of Cu at interfaces while the ternary alloy provides soft magnetic properties and controlled magnetization, achieving both high magneto-resistance ratio and reduced thickness
2Productivity
If the SV film thickness is reduced to meet high linear recording density requirements, then the linear recording density is improved, but it becomes difficult to obtain a sufficient change in magnetic resistance
Solution Approach 1:
The invention optimizes the compositional parameters of the ternary alloy layer in the free layer, specifically controlling the ratio of Ni to total Ni and Fe within 27-45%, and the ratio of Co to total Co, Ni, and Fe within 42-76%. These parameter optimizations enhance the spin scattering efficiency per unit thickness, enabling sufficient magnetic resistance change even with reduced overall film thickness for high linear recording density
3Ease of manufacture
If a conventional free layer structure is used in CPP-GMR elements, then the manufacturing process is simple, but the soft magnetic properties are insufficient for effective magnetic head performance
Solution Approach 1:
The invention employs a composite free layer structure combining Cu and ternary alloy (Co-Fe-Ni) layers. The Cu layer provides high spin scattering at interfaces, while the ternary alloy layer contributes soft magnetic properties including low coercivity and appropriate magnetization. This composite approach maintains manufacturing simplicity through standard sputtering processes while significantly improving soft magnetic properties for effective magnetic head performance
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 allows for a significant reduction in film thickness while achieving a large magneto-resistance ratio and improved soft magnetic properties, suitable for high linear recording densities and enhanced reading performance in magnetic heads.
Implementation Method 1
spin-dependent scattering that is caused in accordance with the relative angle
Implementation Method 2
spin-dependent scattering is not sufficiently caused at the boundaries between layers because sense current is applied in the direction that is perpendicular to the layer surfaces
Data Source
AI summary
A magneto-resistive element has a pinned layer, a free layer, and a spacer layer which is sandwiched between the pinned layer and the free layer. The spacer layer is made of copper. The magneto-resistive element is configured such that sense current is applied in a direction that is perpendicular to layer surfaces. The free layer has: a nonmagnetic layer that includes copper as a main component; and ternary alloy layers each including cobalt (Co), iron (Fe), and nickel (Ni), the ternary alloy layers being disposed on both sides of the nonmagnetic layer. The ternary alloy layer includes nickel and iron at a composition ratio in which a ratio x of an atomic percentage of nickel to a total atomic percentage of nickel and iron is 27%≦x≦45%.