Lanthanide Ferromagnetic Bubble Memory With Submicron Domains
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Solution Overview
Problem
Existing magnetic bubble materials exhibit large bubble sizes and magnetic hardness parameters that are not suitable for commercial computer memory applications, necessitating the development of materials with smaller bubble sizes and κ values greater than √2/2 for efficient data storage.
Innovation Solution
Applying an external magnetic field perpendicular to the surface plane of thin lamellae or films of binary ferromagnetic and ferrimagnetic compounds comprising 3d and/or 4f elements, causing a transition from stripe domains to magnetic bubbles, resulting in materials with diameters below 1 μm and κ > √2/2.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If oxide materials (rare-earth iron garnets, orthoferrites, hexagonal ferrites) are used for magnetic bubble memory, then magnetic bubbles can be formed, but the bubble diameter is larger than 1 μm which is too large for commercial applications
Solution Approach 1:
The invention changes the material parameters by transitioning from oxide materials to metallic hard magnets with specific compositions (Nd2Fe14B, SmCo5, Sm2Fe17, etc.). These materials have different magnetic properties including higher saturation magnetization and appropriate anisotropy energy density, enabling bubble diameters below 1 μm while maintaining stability
Solution Approach 2:
The invention uses composite or intermetallic structures such as Nd2Fe14B, SmCo5, and other rare-earth transition metal compounds. These composite materials combine specific elements to achieve the desired magnetic properties including appropriate κ values and small bubble sizes suitable for commercial memory applications
2Reliability
If metallic hard magnets (Nd2Fe14B, SmCo5) with large Ku are used, then κ > 1 satisfying the stability requirement, but the bubble size must be much smaller than 1 μm which is difficult to achieve
Solution Approach 1:
The invention optimizes material parameters by selecting metallic hard magnets with specific saturation magnetization (Ms) and anisotropy energy density (Ku) values. The κ parameter is controlled to be greater than 1, and through precise composition control, bubble diameters are reduced to below 1 μm while maintaining stability
Solution Approach 2:
The invention creates a dynamic balance between magnetic anisotropy energy and demagnetization energy. By controlling the material composition and microstructure, the system achieves a state where high Ku ensures stability while the optimized Ms and domain structure enable small bubble diameters through controlled magnetic domain formation
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 enables the formation of small magnetic bubbles with diameters ≤500 nm, preferably ≤100 nm, and κ ≥0.9, suitable for high-speed data storage and memory applications.
Implementation Method 1
by applying an external magnetic field with a field direction component perpendicular to the surface plane of a thin lamella or film of a metallic hard magnetic material selected from at least binary ferromagnetic and ferrimagnetic compounds
Implementation Method 2
Magnetic bubbles are tiny movable magnetized cylindrical volumes in a thin magnetic material with uniaxial magnetocrystalline anisotropy (Ku)
Implementation Method 3
Ku must be large enough (preferably Ku≥0.5 MJm−3 at 300 K) to resist the demagnetization energy
Data Source
AI summary
The present invention relates to a metallic hard magnetic material selected from an at least binary ferromagnetic or ferrimagnetic compound, with the metallic hard magnetic material including at least two different elements selected from the group consisting of 3d and 4f elements, where the metallic hard magnetic material is under an external magnetic field B of ≥0.1 T.