Dual Free Layer Magnetic Reader Rear Bias Structure
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Solution Overview
Problem
Conventional magnetic recording read transducers face reliability issues at high densities and low track widths, particularly due to unpredictable bias states in dual free layer sensors, which hinder accurate reading of high-density media.
Innovation Solution
A dual free layer magnetic read transducer design is implemented, where the free layers are biased in a scissor mode using side and rear magnetic bias structures, including soft and hard bias components, to stabilize the magnetic moments and enhance reading accuracy at high densities, with the rear soft bias structure addressing clustering issues and ensuring consistent magnetization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dual free layer magnetic read sensors are used to read high density media, then reading capability for high density media is improved, but reliability becomes poor due to unpredictable bias states
Solution Approach 1:
The patent changes the magnetic parameters by introducing a rear soft magnetic bias structure that applies a controlled bias field to the dual free layers. This soft magnetic material has specific coercivity and saturation magnetization parameters that enable reliable biasing of the free layers in a scissor mode, making the bias state predictable while maintaining high density reading capability
Solution Approach 2:
The patent uses a composite bias structure combining soft magnetic material with specific magnetic properties. The soft magnetic material is positioned adjacent to the dual free layers and works in conjunction with the antiferromagnetic and pinned layers to create a stable bias configuration that ensures reliable operation at high densities
2Quantity of substance
If track width is reduced to below twenty nanometers for high density recording, then storage density is improved, but reliability of the read sensor deteriorates
Solution Approach 1:
The patent applies local quality by positioning the soft magnetic bias structure specifically adjacent to the dual free layers in the region where track width is reduced. This localized biasing provides the necessary magnetic field control exactly where needed, ensuring reliable operation even when the overall track width is reduced to below twenty nanometers for high density storage
3Device complexity
If conventional magnetic bias structures are used, then device complexity is low, but measurement precision deteriorates at high densities
Solution Approach 1:
The patent segments the biasing function by separating the soft magnetic bias structure from the hard magnetic bias structures. The soft magnetic material is positioned specifically to provide the primary bias field to the dual free layers, while other magnetic structures provide additional biasing and shielding functions. This segmentation allows each component to be optimized for its specific function, improving reading accuracy at high densities while keeping the overall device complexity manageable
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 design improves the reliability and performance of magnetic recording read transducers by stabilizing the scissor mode bias, enabling accurate reading of high-density media even at track widths below twenty nanometers, thus enhancing signal quality and consistency.
Implementation Method 1
a rear soft bias magnetic structure between the hard bias structure and the dual free layer sensor
Implementation Method 2
The read sensor 20 is typically a giant magnetoresistive (GMR) sensor or tunneling magnetoresistive (TMR) sensor
Data Source
AI summary
A method and system provide a magnetic read apparatus having an air-bearing surface (ABS). The read apparatus includes a read sensor, a side bias structure and a rear magnetic bias structure. The read sensor includes first and second free layers, a spacer layer and a rear surface opposite to the ABS. The spacer layer is nonmagnetic and between the first and second free layers. The side bias structure is adjacent to the side surface(s) and magnetically biases the first and second free layers to be antiferromagnetically aligned. The rear magnetic bias structure biases the free layers in a scissor mode. The read sensor is between the ABS and the rear magnetic bias structure. The rear magnetic bias structure includes a rear soft magnetic bias structure having a saturation magnetization-thickness product of at least one milli-emu/cm2 and not more than three milli-emu/cm2.