Heusler Alloy Free Layer Magnetostriction Reduction via Metal Diffusion
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Solution Overview
Problem
CPP-GMR heads using Heusler alloys for free layers exhibit high magnetostriction and instability due to stress asymmetry, leading to increased magnetic anisotropy and impaired linear response, which limits their operational stability.
Innovation Solution
A method involving the sequential deposition of a pinned layer, a non-magnetic spacer layer, a spacer adjoining layer with a body-centered cubic structure, and a Heusler alloy layer, with a metal layer like silver or gold inserted between the spacer adjoining layer and the Heusler alloy layer, followed by heat treatment to diffuse the metal and reduce magnetostriction at their interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Heusler alloy is used for the free layer to increase spin polarizability and magneto-resistance ratio, then the MR ratio and output are improved, but magnetostriction increases leading to instability and impaired linear response
Solution Approach 1:
A metal layer (silver, gold, copper, palladium, or platinum) is inserted as an intermediary between the spacer adjoining layer and the Heusler alloy layer. This metal layer acts as a mediator that reduces magnetostriction at the interface through diffusion during heat treatment, allowing the Heusler alloy to maintain its high spin polarizability while limiting the harmful magnetostriction effects
Solution Approach 2:
The invention changes the physical and chemical parameters at the interface by introducing a metal layer with specific properties (high diffusivity, low magnetostriction). Through heat treatment, the metal atoms diffuse into the spacer adjoining layer, altering the local composition and magnetic properties to reduce magnetostriction while preserving the high MR ratio characteristics of the Heusler alloy
2Reliability
If a metal layer is inserted between the spacer adjoining layer and Heusler alloy layer, then magnetostriction is reduced, but the device structure becomes more complex
Solution Approach 1:
The metal layer is applied locally only at the critical interface between the spacer adjoining layer and the Heusler alloy layer, where magnetostriction problems occur. This localized approach addresses the specific problem area without requiring modification of the entire device structure, thus minimizing the increase in overall device complexity while achieving the desired stability improvement
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 approach effectively limits magnetostriction to acceptable levels, maintaining a large MR ratio while enhancing the stability and linear response of the magnetic field detecting element.
Implementation Method 1
heat treating the stacked layers in order to form the free layer out of the spacer adjoining layer, the metal layer, and the Heusler alloy layer
Data Source
AI summary
A method for manufacturing a magnetic field detecting element has the steps of: forming stacked layers by sequentially depositing a pinned layer, a spacer layer, a spacer adjoining layer which is adjacent to the spacer layer, a metal layer, and a Heusler alloy layer in this order, such that the layers adjoin each other; and heat treating the stacked layers in order to form the free layer out of the spacer adjoining layer, the metal layer, and the Heusler alloy layer. The spacer adjoining layer is mainly formed of cobalt and iron, and has a body centered cubic structure, and the metal layer is formed of an element selected from the group consisting of silver, gold, copper, palladium, or platinum, or is formed of an alloy thereof.