Thin Film Magnetic Head Barkhausen Noise Reduction
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Solution Overview
Problem
Existing thin film magnetic heads experience significant Barkhausen noise due to fluctuations in the magnetization direction of the free layer caused by transitions in the domain structure of the magnetic shield layers, which are unstable under external impacts and magnetic field changes.
Innovation Solution
Incorporating a hard magnetic layer or an antiferromagnetic layer between the magnetic shield layers, with the hard magnetic layer on the second end face side and the antiferromagnetic layer in contact with the magnetic shield layers, to stabilize the domain structure by applying a static magnetic field that favors a 4-domain configuration, reducing domain wall energy and transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If magnetic shield layers are provided without additional stabilizing layers, then the structure is simple, but the domain structure is unstable and Barkhausen noise increases
Solution Approach 1:
A hard magnetic layer or antiferromagnetic layer is introduced as an intermediary between the magnetic shield layers to stabilize the domain structure. This intermediary layer prevents unwanted domain wall transitions and suppresses Barkhausen noise by maintaining a stable 4-domain configuration in the magnetic shield layers.
Solution Approach 2:
The magnetic head employs a composite structure combining soft magnetic shield layers with a hard magnetic layer or antiferromagnetic layer. This composite material approach leverages the high coercivity of hard magnetic materials or the exchange coupling properties of antiferromagnetic materials to stabilize the domain structure without significantly increasing overall device complexity.
2Reliability
If the hard magnetic layer is positioned on the second end face side with specific dimensions, then domain structure stability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies optimal parameter ranges for the hard magnetic layer (thickness: 1/3 to 1/2 of the magnetic shield layer thickness, positioned on the second end face side) to achieve domain structure stability. These parameter specifications provide clear manufacturing targets while acknowledging practical fabrication tolerances, balancing performance optimization with manufacturability.
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 effectively reduces Barkhausen noise by maintaining the magnetic shield layers in a stable 4-domain structure, minimizing magnetization direction fluctuations and improving readout performance of the reproducing head.
Implementation Method 1
a hard magnetic layer or an antiferromagnetic layer, particularly, between a pair of magnetic shield layers and on the end face side located opposite to an end face forming a medium-facing surface of the pair of magnetic shield layers
Implementation Method 2
the domain structure of the magnetic shield layers can be stabilized by providing a hard magnetic layer or an antiferromagnetic layer
Implementation Method 3
a thin film magnetic head comprising a magnetoresistive effect element (hereinafter referred to as an MR (MagnetoResistive) element)
Data Source
AI summary
A thin film magnetic head has an air bearing surface and comprises magnetic shield layers, an MR element, bias-applying layers, and a hard magnetic layer. Each of the magnetic shield layers has an end face forming the air bearing surface, and an end face located opposite to the end face. The MR element is located between the magnetic shield layers and on the end face side. The bias-applying layers are located between the magnetic shield layers and are arranged to apply a bias magnetic field to the MR element. The hard magnetic layer is located between the magnetic shield layers and on the end face side. A height of the hard magnetic layer is larger than ⅓ and smaller than ½ of a height of each magnetic shield layer.