US 11138997

Here's a concise summary of US Patent 11138997:

US Patent 11138997: Multilayer exchange spring recording media

• Title: Multilayer exchange spring recording media
• Current Assignee: MR Technologies GmbH
• Inventors: Dieter Suess
• Filing Date: March 19, 2018 (priority date June 17, 2006)
• Issue Date: October 5, 2021
• Abstract: The patent describes a multilayer exchange spring recording media. This media consists of a magnetically hard magnetic storage layer that is strongly exchange coupled to a softer nucleation host. The strong exchange coupling can be direct or facilitated by a coupling layer. The hard magnetic storage layer possesses strong perpendicular anisotropy. The nucleation host comprises one or more ferromagnetic coupled layers, where the anisotropy increases from layer to layer in a multilayer nucleation host. The anisotropy in the softest layer of the nucleation host can be significantly smaller (e.g., two times smaller) than that of the hard magnetic storage layer. The lateral exchange between the grains is kept small. The primary function of the nucleation host is to significantly decrease the coercive field of the media while maintaining the energy barrier of the hard layer almost unchanged. The coercive field of the overall structure is inversely dependent on the number of layers in the nucleation host. This invention aims to overcome the writeability problem encountered in perpendicular recording media.

Plain-language overview of independent claims:

Claim 1: This claim describes a magnetic recording system. It includes a writing head and a disk containing a magnetic recording medium. The medium has:

• An essentially non-magnetic substrate.
• An underlayer formed on this substrate.
• An exchange-coupled magnetic multilayer structure. This structure consists of:
  • A hard magnetic storage layer, with a coercive field greater than 0.5 Tesla (Hs > 0.5 T), formed on the underlayer.
  • A nucleation host, which is formed on the hard magnetic storage layer (meaning the hard magnetic storage layer is between the nucleation host and the substrate). This nucleation host has a coercive field (Hn) that is lower than the hard magnetic storage layer's coercive field (Hn < Hs) when measured without the hard magnetic storage layer. The nucleation host is also exchange-coupled to the hard magnetic storage layer and is composed of ferromagnetic layers where the anisotropy constant (K) increases from one layer to the next.

Claim 7: This claim describes a magnetic recording medium (without specifying the entire system). It includes:

• An essentially non-magnetic substrate.
• An underlayer formed on the non-magnetic substrate.
• An exchange-coupled magnetic multilayer structure. This structure comprises:
  • A hard magnetic storage layer, having a first coercive field (Hs) greater than 0.5 Tesla, formed on the underlayer.
  • A nucleation host, having a second coercive field (Hn) without the hard magnetic storage layer, which is lower than the first coercive field (Hn < Hs). This nucleation host is formed on the hard magnetic storage layer such that the hard magnetic storage layer is positioned between the nucleation host and the non-magnetic substrate. The nucleation host is also exchange-coupled to the hard magnetic storage layer and comprises ferromagnetic layers with an increasing anisotropy constant (K) from layer to layer. A distinguishing feature of this claim is that at least two of these ferromagnetic layers within the nucleation host are coupled together with a thin exchange coupling layer.

Uncertainty Note: The full text of the patent (US11138997) was provided in the prompt, allowing for direct extraction of the abstract and claims. The filing and issue dates were explicitly found on the Google Patents page linked in the original prompt. Information regarding litigation from the search results confirmed the title, assignee, and inventor, and specified that claims 1 and 7 were found infringed in a lawsuit. Therefore, there is high confidence in the provided information.