AFM Grain Growth Control for RTN Suppression in Magnetic Read Heads
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Solution Overview
Problem
Miniaturization of magnetic read heads in hard disk drives leads to increased magnetic instability and random telegraph noise (RTN), causing signal fluctuations and read errors due to the demagnetizing field and reduced sensor sensitivity.
Innovation Solution
Incorporating an antiferromagnetic (AFM) layer with a MnIr alloy in an L12 ordered phase, a pinned layer, and a seed layer with a laminated structure, including Ru, to enhance exchange coupling and stability, thereby reducing RTN and improving signal integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the read head sensor is miniaturized to achieve higher recording densities, then the track width and stripe height are reduced, but the magnetic stability deteriorates and read noise increases
Solution Approach 1:
The patent uses a composite magnetic body structure comprising multiple magnetic layers (first magnetic layer, second magnetic layer, third magnetic layer) with different magnetic properties. The first magnetic layer has higher coercivity than the second and third layers, creating a stable magnetic configuration that maintains reliability even when the overall sensor size is reduced for higher recording densities.
2Productivity
If the read head sensor is miniaturized, then the track width is reduced, but the sensor sensitivity decreases
Solution Approach 1:
The composite magnetic body with three magnetic layers having different coercivities creates enhanced magnetic contrast and signal detection capability. The first magnetic layer with higher coercivity provides stability while the second and third layers with lower coercivity respond more sensitively to external magnetic fields, maintaining measurement precision in miniaturized sensors.
3Productivity
If the stripe height is reduced, then the recording density is increased, but the signal-to-noise ratio deteriorates
Solution Approach 1:
The three-layer magnetic structure with varying coercivities creates a favorable signal response where the first layer provides a stable reference and the second and third layers generate detectable signal changes. This composite structure maintains adequate signal-to-noise ratio even when stripe height is reduced to increase recording density.
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 effectively suppresses random telegraph noise, enhancing the stability of magnetization and reducing read errors, leading to improved signal-to-noise ratio and overall performance of the magnetic read head.
Implementation Method 1
The pinned layer has fixed magnetization by virtue of a strong exchange coupling field from the AFM layer
Implementation Method 2
The magnetic bodies forming the read sensor film may comprise an antiferromagnetic layer
Implementation Method 3
The sensor changes resistance by using a tunneling effect of electrons in an insulated barrier layer, which is referred to as tunneling magnetic resistance (TMR)
Data Source
AI summary
In one embodiment, a magnetic read head includes an antiferromagnetic (AFM) layer including a MnIr alloy having an L12 ordered phase, a pinned layer positioned above the AFM layer, and a seed layer positioned directly below the AFM layer, wherein the seed layer includes a laminated structure with an upper layer including Ru being positioned above one or more additional layers. In another embodiment, a magnetic read head includes an AFM layer including a MnIr alloy having an L12 ordered phase, a pinned layer positioned above the AFM layer, and a seed layer positioned directly below the AFM layer, the seed layer including a laminated structure of Ta/Y/Ru, wherein Y is a layer having an element or an alloy. Other magnetic heads having a reduced amount of random telegraph noise (RTN) and methods of formation thereof are disclosed according to more embodiments.