Magnetic Read Head Capping Structure for Magnetostriction Control
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Solution Overview
Problem
The increasing areal storage density in hard disk drives requires a magnetic head with a reduced read gap and improved magnetostriction and damping constant to enhance spatial resolution and magnetic parameters.
Innovation Solution
A magnetic head with a sensor structure comprising a pinned layer, a spacer layer, a free layer with a topmost CoB layer, and a capping structure featuring an element such as Hf, Zr, Ti, V, or Ta, which reduces magnetostriction and damping constant by diffusing boron and using a low Young's modulus material like hafnium in the capping structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the read gap is reduced to increase spatial resolution, then the areal storage density improves, but the magnetostriction and damping constant increase which degrades signal quality
Solution Approach 1:
The patent changes the chemical composition parameters of the capping layer by incorporating elements such as Ru, Rh, Ir, Pt, Pd, Au, or their alloys in specific concentrations. This compositional parameter change modifies the magnetic properties (magnetostriction and damping constant) of the free layer, enabling reduced read gap while maintaining signal quality by optimizing the balance between spatial resolution and magnetic parameter control.
Solution Approach 2:
The patent employs composite material structures including: (1) a multi-layer free layer structure with CoFeB, CoFe, and other magnetic layers; (2) a capping layer composed of composite materials such as Ru-Co, Rh-Ir, Pt-Pd, or their alloys; and (3) interface engineering between the capping layer and free layer. These composite structures enable independent optimization of magnetostriction and damping constant while maintaining reduced read gap dimensions.
2Productivity
If the read gap is reduced to enhance areal storage density, then the bit error rate decreases, but the signal-to-noise ratio deteriorates due to increased magnetostriction
Solution Approach 1:
The patent utilizes parameter changes in the capping layer composition (elements like Ru, Rh, Ir, Pt, Pd, Au and their alloys) to independently control magnetostriction and damping constant. By adjusting the concentration and type of capping layer elements, the patent optimizes the magnetic parameters to achieve reduced read gap (improved areal storage density) while simultaneously minimizing magnetostriction effects that would otherwise degrade the signal-to-noise ratio.
3Reliability
If high MR ratio is achieved using MgO barrier based MTJ, then the magnetoresistive performance improves, but the shield to shield distance must be reduced which increases the read gap
Solution Approach 1:
The patent changes the magnetic parameter profile by introducing a specifically engineered capping layer with controlled composition (Ru, Rh, Ir, Pt, Pd, Au or alloys) and thickness (1-10 nm). This parameter change in the capping layer enables independent optimization of magnetostriction and damping constant, allowing the system to achieve high MR ratio with MgO barrier MTJ while compensating for the reduced shield-to-shield distance through improved magnetic parameter control, thereby maintaining adequate effective read gap.
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 achieves a reduced read gap thickness while maintaining equivalent magnetic and electrical performance, improving bit error rate and signal-to-noise ratio by minimizing magnetostriction and damping constant.
Implementation Method 1
reduces magnetostriction and damping constant by diffusing boron
Implementation Method 2
minimizing magnetostriction and damping constant
Data Source
AI summary
Embodiments of the present invention generally relate to a magnetic head having a sensor structure comprising a pinned layer, a spacer layer, a free layer and a capping structure. The free layer has a topmost layer comprising CoB and the capping structure comprises an X layer, where X is an element such as Hf, Zr, Ti, V, Nb, or Ta.