Perpendicular Magnetic Recording Medium Seed Layer Design
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Solution Overview
Problem
Current methods for manufacturing perpendicular magnetic recording media face challenges in controlling the orientation of the easy axis of magnetization and reducing the ordering temperature of ordered alloys like FePt without compromising magnetic anisotropy, which is essential for achieving high recording density and thermal stability.
Innovation Solution
A method involving the formation of a nonmagnetic seed layer with a MgO layer and a metal layer having a body-centered cubic structure, along with a nonmagnetic underlayer with a NaCl type structure, to achieve controlled crystal orientation and reduce the ordering temperature to 350°C or lower, allowing for the growth of FePt, FePd, or CoPt alloys with a large Ku value without heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional CoCr-based materials are used for perpendicular magnetic recording, then manufacturing process is simple, but magnetic anisotropy is insufficient leading to thermal fluctuation problems
Solution Approach 1:
The patent changes the material parameter from conventional CoCr-based alloys to ordered L10-type alloys (FePt, CoPt, FePd) with specific composition ratios and crystal structures. This parameter change enables achieving the required magnetic anisotropy (Ku ≥ 4×10^7 erg/cm³) for thermal stability while maintaining manufacturability through controlled deposition processes
Solution Approach 2:
The patent employs composite material structures combining multiple layers with specific functions: L10-type ordered alloy magnetic layers for high anisotropy, nonmagnetic underlayers (Ru, Pd, Pt) for orientation control, and seed layers for crystal orientation. This composite approach resolves the contradiction by integrating materials that collectively provide both thermal stability and manufacturability
2Reliability
If high-temperature heating is applied to form ordered alloy structure, then magnetic anisotropy is improved, but manufacturing process becomes complex and time-consuming
Solution Approach 1:
The patent applies preliminary action by forming seed layers and underlayers with specific crystal orientations before depositing the L10-type ordered alloy. The seed layers are prepared in advance to establish the desired (001) or (002) crystal orientation, which then guides the formation of the magnetic layer without requiring subsequent high-temperature heating, thus reducing manufacturing time while maintaining magnetic anisotropy
Solution Approach 2:
The patent replaces the thermal field (high-temperature heating) with a structural field (crystal orientation control through seed layers and underlayers). By using carefully designed layered structures with specific crystal orientations, the patent achieves ordered alloy formation without relying on thermal energy, thereby eliminating the time-consuming heating process
3Manufacturing precision
If easy axis orientation is not controlled, then manufacturing is simpler, but recording density and thermal stability are compromised
Solution Approach 1:
The patent segments the magnetic recording medium into distinct functional layers: seed layers with specific crystal orientations, nonmagnetic underlayers for orientation control, and L10-type ordered alloy magnetic layers. Each segment serves a specific purpose in controlling the easy axis orientation, achieving precise crystal orientation control through modular layer design without excessive overall complexity
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 approach enables the production of perpendicular magnetic recording media with controlled crystal orientation and high magnetic anisotropy, facilitating the formation of thin films with improved thermal stability and recording density, while simplifying the manufacturing process by avoiding the need for high-temperature heating.
Implementation Method 1
Such ordered alloy-based materials have an ordered phase formed of, for example, at least one magnetic element selected from Fe, Co, and Ni, and at least one noble metal element selected from Pt, Pd, Au, and Ir. Particularly, FePt and CoPt, ordered alloys having a fct crystal structure, are known to have a magnetic anisotropy as large as 7×10^7 erg/cm³ and 4×10^7 erg/cm³, respectively, in a c-axis direction that is an easy axis of magnetization.
Implementation Method 2
The nonmagnetic seed layer includes a MgO layer and a metal layer having a body-centered cubic (bcc) structure. The nonmagnetic underlayer has a NaCl type structure of one selected from the group consisting of MgO, NiO, TiO, CrN, Ti carbides, and Ti nitrides. All of a (001) crystal lattice plane of the metal layer, a (001) crystal lattice plane of the NaCl type structure in the nonmagnetic underlayer, and a (001) crystal lattice plane of the L10 type ordered structure in the magnetic layer are preferably parallel to a film surface.
Data Source
AI summary
Provided are a perpendicular magnetic recording medium and a method for manufacturing the same, the perpendicular magnetic recording medium including an alloy (FePt, FePd, or CoPt) having a large Ku value with an L10 type ordered structure, and obtained with achievement of controlled crystal orientation and thin film formation without heating. Specifically, in the perpendicular magnetic recording medium, at least a nonmagnetic seed layer, a nonmagnetic underlayer, and a magnetic layer are formed in this order on a nonmagnetic substrate. The nonmagnetic seed layer includes a MgO layer and a metal layer having a body-centered cubic (bcc) structure. The nonmagnetic underlayer has a NaCl type structure of one selected from the group consisting of MgO, NiO, TiO, CrN, Ti carbides, and Ti nitrides. The magnetic layer includes an alloy selected from the group consisting of FePt, FePd, and CoPt having an L10 type ordered structure.