Non-magnetic Insertion Layer for Read Gap Protrusion in Magnetic Heads
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Solution Overview
Problem
Current magnetic recording heads face challenges in achieving optimal read gap protrusion and write current-driven protrusion while maintaining magnetic performance and avoiding corrosion, as the thickness of the lower read shield (S1) layer can lead to undesirable magnetic characteristics and increased hysteresis rejection rates.
Innovation Solution
A non-magnetic layer with high thermal expansion coefficient (CTE) and conductivity is inserted below the S1 shield in the read head, recessed from the air bearing surface, to enhance read gap protrusion and act as a heat sink, maintaining the S1 thickness and avoiding adverse magnetic effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the lower read shield (S1) layer thickness is increased to improve read gap protrusion, then read gap protrusion efficiency is improved, but magnetic characteristics deteriorate and hysteresis rejection rates increase
Solution Approach 1:
A non-magnetic insertion layer with high CTE is introduced between the heater and the S1 shield as an intermediary element. This insertion layer mediates the thermal expansion process, providing enhanced read gap protrusion without requiring increased S1 thickness, thereby preserving magnetic characteristics while improving protrusion efficiency
Solution Approach 2:
The invention changes the thermal expansion parameter by introducing a material with high CTE (coefficient of thermal expansion) into the structure. This parameter change enables greater dimensional change in response to thermal input, achieving improved read gap protrusion without increasing the S1 shield thickness
2Productivity
If dynamic flying height power is applied to actuate the reader to achieve optimal read gap protrusion, then read performance is improved, but temperature rise occurs affecting write current driven protrusion
Solution Approach 1:
The invention exploits thermal expansion by using a non-magnetic layer with high CTE that expands significantly when heated by the heater. This thermal expansion directly drives the read gap protrusion, improving read performance while the controlled geometry of the insertion layer manages the overall temperature rise in the structure
3Force
If write current is increased to improve write current driven protrusion, then write field strength is improved, but excessive temperature rise occurs
Solution Approach 1:
The non-magnetic insertion layer acts as a thermal mediator that facilitates more efficient heat distribution. This intermediary structure helps manage the thermal load from write current, allowing for improved write field strength while controlling excessive temperature rise through better thermal management
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 configuration allows for efficient read gap protrusion at the same power level, improving the gamma parameter and dynamic performance without compromising magnetic characteristics, and provides a superior heat sink for write current-driven protrusion, achieving a gamma ratio closer to 1 and reduced dynamic fly height temperature rise.
Implementation Method 1
a non-magnetic layer with a high coefficient of thermal expansion (CTE) and high thermal conductivity is formed within an insulation layer below the bottom (S1) shield in the read head to enhance read gap (RG) protrusion at the same power
Implementation Method 2
serve as a superior heat sink for improved write current (Iw) driven protrusion
Implementation Method 3
The joule heating from the electrical current into the heater film is conducted away from the source
Data Source
AI summary
A read/write head is disclosed wherein a non-magnetic layer made of a metal is inserted in the read head on a side opposite to the S1 shield with respect to the sensor. The non-magnetic layer is preferably Cu and is recessed from the ABS to prevent corrosion. A preferred design has a 1 to 5 micron thick non-magnetic insertion layer that extends a distance of 3 to 100 microns along a plane that is perpendicular to the ABS. RG efficiency is enhanced significantly and RG gamma ratio is improved to 1.0 so that a smaller difference in RG, WG, and min-fly point can be achieved at touchdown detection and in normal read/write operations. These results lead to an optimal dynamic performance for a given spacing target and enhanced read gap protrusion at a given heater power. S1/S2A thickness can be independently optimized for magnetic performance consideration only.