Magnetic Disk Auxiliary Recording Layer Oxygen Content
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Solution Overview
Problem
Conventional magnetic disks with recording capacities above 250 G bits per square inch experience noise due to strong exchange interaction between magnetic particles in the auxiliary recording layer, which is a continuous film, leading to reduced signal quality and thermal instability.
Innovation Solution
A magnetic disk with a granular magnetic recording layer and an auxiliary recording layer containing 0.1 to 3 mol % oxygen, where the auxiliary recording layer is formed on the granular magnetic recording layer to improve grain boundary uniformity and reduce noise, and a granular auxiliary recording layer with higher coercive force acts as a pin layer to narrow track width and enhance signal-to-noise ratio (SNR).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the recording capacity is increased to 250 G bits per square inch or more using a continuous film auxiliary recording layer, then the exchange interaction between magnetic particles strengthens, but noise is caused due to strong exchange interaction
Solution Approach 1:
The patent changes the chemical composition parameter of the auxiliary recording layer by adding oxygen (0.1 to 3 mol%) to modify the magnetic properties. This parameter change reduces the exchange interaction strength between magnetic particles, thereby suppressing noise generation while maintaining high recording capacity of 250 G bits per square inch or more
Solution Approach 2:
The patent creates a composite auxiliary recording layer by combining magnetic particles with oxygen-containing compounds or oxides. This composite structure modifies the magnetic continuity and exchange interaction characteristics, reducing noise while preserving the necessary magnetic properties for high-density recording
2Measurement precision
If the particle diameter of magnetic particles is reduced to improve SNR, then the SNR improves, but thermal stability deteriorates
Solution Approach 1:
The patent changes the magnetic anisotropy energy parameter (Ku) by introducing oxygen into the auxiliary recording layer. This allows achieving thermal stability with smaller particle diameters by enhancing the perpendicular magnetic anisotropy through oxygen-induced modifications in the auxiliary layer's magnetic properties
Solution Approach 2:
The oxygen-containing auxiliary recording layer acts as an intermediary that mediates between the magnetic recording layer and the external environment. It provides exchange coupling that enhances thermal stability without requiring larger particle diameters, thus maintaining high SNR while improving thermal stability
3Stability of the object's composition
If perpendicular magnetic anisotropy energy (Ku) is increased to thermally stabilize a signal, then thermal stability improves, but recording becomes impossible due to excessive Ku
Solution Approach 1:
The patent precisely controls the oxygen content parameter (0.1 to 3 mol%) in the auxiliary recording layer to achieve optimal perpendicular magnetic anisotropy energy. This controlled parameter adjustment ensures sufficient thermal stability while maintaining Ku values that allow successful recording with magnetic heads
Solution Approach 2:
The patent applies partial oxidation by limiting oxygen content to 0.1 to 3 mol% rather than full oxidation. This partial action provides enough exchange coupling and thermal stability enhancement without excessive Ku increase that would prevent recording, achieving the optimal balance between thermal stability and recordability
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 magnetic disk achieves reduced noise and improved SNR even at high recording capacities by optimizing the auxiliary recording layer composition and structure, maintaining film thickness to balance track width and SNR, thereby enhancing recording density and thermal stability.
Implementation Method 1
the oxygen is preferably contained in the auxiliary recording layer in a state of oxide. Here, the oxide is preferably precipitated on the non-magnetic regions of the granular magnetic recording layer.
Implementation Method 2
an auxiliary recording layer which is formed on the granular magnetic recording layer and which causes exchange coupling among the granular columnar particles
Data Source
AI summary
Provided are a magnetic disk comprising a granular magnetic recording layer which causes less noise even with a recording capacity thereof of 250 G or more bits per square inch; and a method for manufacturing the same. The magnetic disk according to the present invention comprises: a granular magnetic recording layer (20) which is formed on a disk substrate 10 directly or via an intermediate layer and which has non-magnetic regions between granular columnar particles; and an auxiliary recording layer (22) which is formed on the granular magnetic recording layer 20 and which causes exchange interaction among the granular columnar particles, wherein the auxiliary recording layer (22) contains 0.1 to 3 moles of oxygen.