IP Verse

Multilayer Exchange Spring Recording Media

Patent No. US12020734 (titled "Multilayer Exchange Spring Recording Media") was filed by Mr Technologies Gmbh on Oct 4, 2021.

What is this patent about?

’734 is related to the field of magnetic data storage , specifically addressing the challenge of increasing storage density in magnetic recording media. The background involves overcoming the superparamagnetic limit, where thermal fluctuations destabilize small magnetic grains, while also ensuring the media remains writable with existing recording heads. This requires balancing thermal stability (high anisotropy) with writeability (lower coercivity).

The underlying idea behind ’734 is to decouple the thermal stability and writeability requirements in magnetic recording media by using a multilayer structure with a hard magnetic storage layer exchange coupled to a softer nucleation host . The nucleation host facilitates domain wall formation and propagation during writing, effectively reducing the coercive field needed to switch the hard layer's magnetization, without significantly compromising the hard layer's thermal stability.

The claims of ’734 focus on a magnetic recording system that includes a writing head and a disk. The disk incorporates a magnetic recording medium with an essentially non-magnetic substrate, an underlayer, and an exchange-coupled magnetic multilayer structure. This multilayer structure comprises a hard magnetic storage layer with perpendicular anisotropy and a coercive field greater than 0.5T, and a nucleation host with a lower coercive field than the hard layer.

In practice, the invention involves carefully selecting materials and thicknesses for the hard magnetic storage layer and the nucleation host. The anisotropy of the nucleation host can be uniform or graded , with multiple layers of increasing anisotropy or a continuously varying anisotropy profile. The exchange coupling between the layers is strong, enabling domain wall formation across the interface during reversal. The lateral exchange between grains is controlled to optimize domain wall pinning and propagation.

This approach differentiates itself from prior solutions by separating the functions of thermal stability and writeability . Earlier methods often involved compromises, such as reducing the anisotropy of the entire grain or using heat-assisted recording. By using a multilayer structure with a softer nucleation host, the invention allows for a high-anisotropy hard layer for thermal stability, while the nucleation host reduces the switching field required for writing, leading to improved performance and higher storage densities.

How does this patent fit in bigger picture?

Technical landscape at the time

In the mid-2000s when ’734 was filed, magnetic storage systems commonly relied on increasing areal density to improve performance, at a time when the superparamagnetic limit posed a significant constraint on further density increases. Overcoming this limit by increasing the anisotropy constant K resulted in unfavorable increases in coercivity, making writing data difficult with existing recording heads. At a time when multilayer structures and exchange spring media were being explored, achieving optimal thermal stability and writeability remained a challenge due to the complex interplay of layer architectures and anisotropies.

Novelty and Inventive Step

The examiner approved the application because the prior art, specifically the Suess et al. reference, did not teach or suggest the specific coercive field and exchange coupling relationship between the nucleation host and hard magnetic storage layer, nor did it disclose a nucleation host comprising first and second ferromagnetic layers with the claimed anisotropy constant relationship (K1 and K2).

Claims

This patent contains 12 claims, with claim 1 being the only independent claim. Independent claim 1 is directed to a magnetic recording system with a writing head and a disk that includes a magnetic recording medium having a specific multilayer structure. The dependent claims elaborate on the composition, configuration, and properties of the magnetic recording system described in independent claim 1.

Key Claim Terms New

Definitions of key terms used in the patent claims.

Term (Source)Support for SpecificationInterpretation
Exchange coupled magnetic multilayer structure
(Claim 1)		“Briefly and generally, embodiments according to the invention include a magnetic recording media wherein the magnetic recording layer consists of a multilayer structure, with a special multilayer host layer (nucleation host) and a hard magnetic storage layer (H c>2 T). The layers can be strongly exchange coupled. The exchange coupling can be direct or via a thin coupling layer in order to achieve strong coupling. If the layers are strongly coupled a domain wall is formed across the hard/soft interface during reversal.”A magnetic recording medium with multiple layers that are magnetically linked together through exchange interactions.
Hard magnetic storage layer
(Claim 1)		“Briefly and generally, embodiments according to the invention include a magnetic recording media wherein the magnetic recording layer consists of a multilayer structure, with a special multilayer host layer (nucleation host) and a hard magnetic storage layer (H c>2 T). During writing a domain wall is formed in the nucleation host that propagates through the whole grain structure and finally reverses the hard magnetic storage layer. In some embodiments the host layer comprises of just one layer, the media is a bilayer structure with one hard magnetic nucleation host and an even harder storage layer.”A layer of the magnetic recording medium with high coercivity, used for storing data.
Nucleation host
(Claim 1)		“Briefly and generally, embodiments according to the invention include a magnetic recording media wherein the magnetic recording layer consists of a multilayer structure, with a special multilayer host layer (nucleation host) and a hard magnetic storage layer (H c>2 T). The anisotropy of the softest layer in the nucleation host is significantly smaller than in the hard layer. During writing a domain wall is formed in the nucleation host that propagates through the whole grain structure and finally reverses the hard magnetic storage layer. In some embodiments the host layer comprises of just one layer, the media is a bilayer structure with one hard magnetic nucleation host and an even harder storage layer.”A layer in the magnetic recording medium that facilitates the reversal of the hard magnetic storage layer.
Perpendicular anisotropy material
(Claim 1)		“Modern magnetic recording media reaches ever higher recording densities. In the paper “Composite Media for Perpendicular Magnetic Recording”, IEEE Transcations on Magnetics, Vol. 41, No. 2, February 2005, pp. 537-542, R. H. Victora and X. Shen proposed magnetic multilayer structures composed of magnetically hard and magnetically soft layers.”A material with a preferred magnetization direction perpendicular to the plane of the film.

Patent Family

Patent Family

File Wrapper

The dossier documents provide a comprehensive record of the patent's prosecution history - including filings, correspondence, and decisions made by patent offices - and are crucial for understanding the patent's legal journey and any challenges it may have faced during examination.

  • Date

    Description

  • Get instant alerts for new documents

US12020734

MR TECHNOLOGIES GMBH
Application Number
US17492735
Filing Date
Oct 4, 2021
Status
Granted
Expiry Date
Jun 17, 2026
External Links
Slate, USPTO, Google Patents