HAMR Medium MgNiO Intermediate Layer Corrosion Resistance
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Solution Overview
Problem
The use of MgO as an underlayer in heat-assisted magnetic recording (HAMR) media leads to corrosion issues due to its sensitivity and reactivity with moisture, causing surface defects and severe head-disk interface problems.
Innovation Solution
A HAMR medium with a heat-sink layer and a chemically-ordered FePt or CoPt alloy magnetic layer, incorporating a MgNiO intermediate layer of the form (Mg(100-y)Niy)O, where y is less than 10 and greater than or equal to 0.5, which functions as both a seed layer and a thermal barrier, replacing the pure MgO underlayer to enhance corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pure MgO is used as an underlayer in HAMR media, then thermal barrier function and seed layer function are achieved, but corrosion resistance deteriorates due to moisture sensitivity and reactivity
Solution Approach 1:
A gradient buffer layer with composition MgO(100-x)Tix is introduced between the MgO underlayer and the FePt/CoPt magnetic layer. This intermediary layer acts as a protective barrier that reduces moisture sensitivity and prevents direct contact between moisture and the pure MgO layer, thereby improving corrosion resistance while maintaining the thermal barrier and seed layer functions.
Solution Approach 2:
The underlayer structure is transformed from pure MgO to a composite structure consisting of MgO(100-x)Tix gradient buffer layer and pure MgO layer. This composite material combines the advantages of both materials: MgO provides thermal barrier function and TiO2 provides improved moisture resistance, achieving both thermal isolation and corrosion protection.
2Stability of the object's composition
If high Ku magnetic material is used to avoid superparamagnetic effect, then thermal stability improves, but coercivity increases beyond write head capability
Solution Approach 1:
The magnetic layer composition is optimized by adjusting the Fe:Pt or Co:Pt ratio and controlling the chemical ordering to achieve the desired L10 phase structure. This parameter optimization allows achieving high Ku for thermal stability while maintaining coercivity within write head capabilities through precise compositional control.
Solution Approach 2:
The magnetic layer is designed with specific local structural characteristics including chemically ordered L10 phase regions with perpendicular magnetic anisotropy. The local chemical ordering and crystal structure are optimized to provide high thermal stability in specific regions while maintaining overall magnetic properties within write capability.
3Strength
If FePt alloy is deposited at high temperature to achieve L10 phase ordering, then magnetic properties improve, but manufacturing complexity increases
Solution Approach 1:
The MgO(100-x)Tix gradient buffer layer is deposited beforehand to prepare the substrate surface with optimal properties for subsequent FePt/CoPt magnetic layer deposition. This preliminary layer facilitates easier deposition conditions and helps achieve the desired L10 phase ordering at reduced temperatures by providing a suitable crystalline template and stress control.
Solution Approach 2:
The deposition temperature parameter is optimized by introducing the MgO(100-x)Tix gradient buffer layer, which modifies the thermal and structural properties of the substrate. This allows achieving L10 phase ordering at lower temperatures than conventional direct deposition on MgO, reducing manufacturing complexity while maintaining magnetic properties.
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 HAMR medium with the MgNiO intermediate layer exhibits significantly improved corrosion resistance compared to prior art, with reduced surface defects and minimal impact on magnetic properties, maintaining thermal stability and write field capability.
Implementation Method 1
a thermal barrier layer
Implementation Method 2
a seed layer to induce the desirable (001) texture
Implementation Method 3
chemically-ordered in the L10 phase
Implementation Method 4
perpendicular magnetic anisotropy
Implementation Method 5
heat-sink layer
Data Source
AI summary
A heat-assisted magnetic recording (HAMR) medium has a heat-sink layer, a chemically-ordered FePt (or CoPt) alloy magnetic layer and a MgNiO intermediate layer between the heat-sink layer and the magnetic layer. The intermediate layer is a solid substitution crystalline alloy of the form (Mg(100-y)Niy)O, where y is less than 10 and greater than or equal to 0.5. The magnetic layer may be formed directly on the MgNiO intermediate layer, in which case the MgNiO intermediate layer functions as both a seed layer and a thermal barrier layer. The HAMR medium may also include an optional layer of crystalline “pure” MgO directly below or directly above the MgNiO intermediate layer. If the MgO layer is located directly above the MgNiO intermediate layer then the MgNiO intermediate layer functions primarily as a thermal barrier layer. The HAMR medium with the MgNiO intermediate layer provides a substantial improvement in corrosion resistance.