Soft-Magnetic-Particle Protective Layer for Perpendicular Recording Media
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Solution Overview
Problem
Narrow-track recording heads in hard disk drives face challenges in generating a sufficiently strong recording magnetic field due to physical deterioration from contamination caused by frictional wear when the head is too close to the medium, leading to insufficient signal/noise ratio and overwrite ability.
Innovation Solution
A perpendicular magnetic recording medium is designed with a substrate, an undercoat layer of soft magnetic material, a recording layer with perpendicular magnetization, and a protective layer mixed with soft magnetic particles, which enhances the magnetic field strength and gradient, allowing for higher line density and resolution while preventing physical deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the recording head is set closer to the medium to increase recording magnetic field intensity, then the recording magnetic field strength is improved, but physical deterioration occurs due to contamination from frictional wear
Solution Approach 1:
A protective layer comprising a nonmagnetic layer and a magnetic layer is introduced as an intermediary between the recording head and the recording layer. This protective layer reduces frictional wear and contamination while maintaining effective magnetic coupling, allowing the recording head to operate at an optimal distance without direct contact damage.
Solution Approach 2:
The protective layer is constructed as a composite structure with a nonmagnetic layer (reducing friction and wear) and a magnetic layer (maintaining magnetic coupling). This composite material approach enables simultaneous achievement of reduced physical deterioration and sufficient recording magnetic field strength.
2Area of stationary object
If a narrow-track recording head is used to increase track density, then the track density is improved, but the recording magnetic field intensity becomes insufficient
Solution Approach 1:
The magnetic layer in the protective layer is designed with specific local properties (magnetic permeability and thickness) to concentrate and enhance the recording magnetic field locally at the track position, compensating for the reduced field intensity caused by narrow track width.
Solution Approach 2:
By adjusting the thickness and magnetic permeability parameters of the magnetic layer in the protective layer, the recording magnetic field intensity is optimized for narrow-track applications, enabling sufficient field strength despite reduced track density spacing.
3Reliability
If the protective layer is made thicker to prevent physical deterioration, then the protection against frictional wear is improved, but the magnetic field gradient and line density are reduced
Solution Approach 1:
The thickness of the protective layer is optimized within a specific range (1-10 nm for the nonmagnetic layer and 2-20 nm for the magnetic layer) to balance protective function and magnetic performance. This parameter optimization ensures adequate wear protection while maintaining sufficient magnetic field gradient for high line density recording.
Solution Approach 2:
The composite structure of nonmagnetic and magnetic layers provides enhanced protection against frictional wear while the magnetic layer maintains effective magnetic coupling, achieving both durability and high-resolution recording capabilities.
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 increases the maximum magnetic field strength and gradient, enabling high line density and superior overwrite characteristics while preventing physical deterioration of the recording head and medium.
Implementation Method 1
a protective layer which is formed on the recording layer and in which soft magnetic particles are mixed
Implementation Method 2
a main recording layer having such perpendicular magnetic anisotropy that the anisotropic magnetic field strength is Hk1
Data Source
AI summary
According to one embodiment, a perpendicular magnetic recording medium characterized by includes: a substrate; an undercoat layer formed on the substrate and made of a soft magnetic material; a recording layer formed on the undercoat layer and having an easy axis of magnetization in a direction that is approximately perpendicular to a surface of the perpendicular magnetic recording medium; and a protective layer which is formed on the recording layer and in which soft magnetic particles are mixed.