Composite Thin-Film Magnetic Head Crosstalk Reduction
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Solution Overview
Problem
In thin-film magnetic heads, crosstalk and external noise issues arise due to parasitic capacitance and heat transmission between the inductive write head and MR read head elements, leading to degradation of magnetic characteristics and reduced reliability.
Innovation Solution
A composite thin-film magnetic head design with an additional shield layer between the write head and read head elements, along with a nonmagnetic conductive layer, is implemented to equalize parasitic capacitance and reduce heat transmission, thereby minimizing crosstalk and external noise effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the distance between the inductive write head element and the MR read head element is reduced to minimize heat transmission, then heat-related issues are reduced, but crosstalk voltage and external noise effects increase due to parasitic capacitance
Solution Approach 1:
A nonmagnetic conductive layer is introduced as an intermediary between the write head element and the MR read head element. This layer serves as a mediator that equalizes parasitic capacitance and reduces both heat transmission and crosstalk voltage, allowing the head elements to be positioned closer together without increasing harmful effects.
Solution Approach 2:
The invention changes the electrical and thermal parameters of the structure by adding the nonmagnetic conductive layer. This modifies the parasitic capacitance, heat conduction, and electromagnetic coupling characteristics, enabling optimized positioning of the head elements to balance heat reduction and crosstalk minimization.
2Productivity
If the read gap is narrowed to improve recording density, then higher density recording is achieved, but short-circuit between the magnetic shield layer and the MR layer occurs in CIP-structure GMR heads
Solution Approach 1:
The invention replaces the CIP-structure GMR head with a CPP-structure GMR head, changing the current flow direction from in-plane to perpendicular. This substitution eliminates the short-circuit problem between the magnetic shield layer and MR layer while enabling narrower read gaps for higher recording density.
Solution Approach 2:
The current flow direction is inverted from parallel to perpendicular relative to the laminated layer surfaces. This inversion fundamentally changes the electrical isolation characteristics, allowing the magnetic shield layer to serve as an electrode without risk of short-circuit, thus enabling reduced read gap for higher density.
3Measurement precision
If miniaturization of the magnetic head element is pursued to increase current density and improve performance, then higher sensitivity is achieved, but heat dispersion decreases and crosstalk increases
Solution Approach 1:
The nonmagnetic conductive layer acts as a thermal intermediary that facilitates heat dispersion from the miniaturized write head element to the substrate, preventing heat accumulation. Simultaneously, it serves as an electromagnetic intermediary that reduces crosstalk between the miniaturized head elements, allowing higher current densities without excessive heat or interference.
Solution Approach 2:
The addition of the nonmagnetic conductive layer changes the thermal and electrical parameters of the miniaturized structure. It improves heat conduction to the substrate and modifies electromagnetic coupling, enabling miniaturization to achieve higher sensitivity while controlling heat dispersion and crosstalk effects.
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 design effectively reduces crosstalk voltage, prevents degradation of magnetic properties, and enhances the reliability of the read head element by canceling out external noise and heat-related issues, ensuring stable operation.
Implementation Method 1
a crosstalk voltage is produced across the read head element... because the lower and upper shield layers are used as electrodes and therefore a parasitic capacitance between the write coil and the upper shield layer certainly becomes larger
Implementation Method 2
heat produced by the inductive write head element... transmission of the heat produced at the write head element to the read head element
Implementation Method 3
a sense current flows in a direction perpendicular to surfaces of laminated layers... in the CPP-structure head, a short-circuit between the magnetic shield layer and the MR layer
Implementation Method 4
inductive write head element... provided with a first magnetic pole layer, a nonmagnetic layer, a second magnetic pole layer and a write coil
Implementation Method 5
a heater is provided in each thin-film magnetic head to thermally expand these head element regions... the more downsizing in the HDD apparatus causes a problem of crosstalk between a writing side and a reading side
Data Source
AI summary
A composite thin-film magnetic head includes a substrate, an under layer formed on the substrate, an MR read head element formed on the under layer and provided with a lower shield layer, an upper shield layer and an MR layer in which a sense current flows in a direction perpendicular to a surface of the MR layer through the upper shield layer and the lower shield layer, an inter-shield insulation layer laminated on the MR read head element, an inductive write head element formed on the inter-shield insulation layer and provided with a first magnetic pole layer, a nonmagnetic layer, a second magnetic pole layer whose end portion is opposed to an end portion of the first magnetic pole layer through the nonmagnetic layer, and a write coil, and an additional shield layer formed between the upper shield layer and the first magnetic pole layer.