Prior art

Here is an analysis of the most relevant patent prior art cited by US9928864, including full citations, dates, brief descriptions, and potential claims anticipated under 35 U.S.C. § 102. The analysis focuses on disclosures explicitly mentioned within the text of US9928864, particularly in the "Description of Related Art" and the "Patent Citations" sections.

The core inventive concept of US9928864, as captured in Claim 1, involves a magnetic recording medium comprising an exchange-coupled magnetic multilayer structure where a hard magnetic storage layer is formed on an underlayer, and a nucleation host is formed on the hard magnetic storage layer. A key distinguishing feature highlighted is that the nucleation host itself comprises ferromagnetic layers with increasing anisotropy constant K from layer to layer.

Prior Art Analysis

1. US Pat. No. 5,583,727 (U.S. Pat. No. 5,583,727 A)

• Full Citation: US5583727A - Multiple data layer magnetic recording data storage system with digital magnetoresistive read sensor
• Publication/Filing Date: Priority date: 1995-05-15; Publication date: 1996-12-10.
• Brief Description: This patent "proposed to overcome the problem by employing thermally assisted recording."
• Potential Anticipation: This patent primarily addresses thermally assisted recording, a different approach to the writeability problem than the exchange spring mechanism with a specific anisotropic nucleation host described in US9928864. It does not appear to disclose the specific multilayer structure with a nucleation host having increasing anisotropy from layer to layer, nor its arrangement relative to a hard magnetic storage layer, as claimed in US9928864. Therefore, it is unlikely to anticipate Claim 1 or other claims detailing the specific multilayer structure and anisotropy gradient of US9928864.

2. US Pat. No. 6,280,813 (U.S. Pat. No. 6,280,813 B1)

• Full Citation: US6280813B1 - Magnetic recording media with antiferromagnetically coupled ferromagnetic films as the recording layer
• Publication/Filing Date: Priority date: 1999-10-08; Publication date: 2001-08-28.
• Brief Description: This patent "addressed the thermal instability problem by replacing the conventional single magnetic recording layer with two ferromagnetic films that are antiferromagnetically coupled together across a nonferromagnetic spacer film". This design aimed to reduce the demagnetizing field in longitudinal magnetic recording.
• Potential Anticipation: While it deals with thermal instability using coupled ferromagnetic films, the specific structure described in US9928864's Claim 1 (a nucleation host with increasing anisotropy constant K from layer to layer, formed on a hard magnetic storage layer) is not evident from this description. The coupling described is "antiferromagnetically coupled together across a nonferromagnetic spacer film," which is different from the exchange-coupled hard layer/nucleation host structure and anisotropy gradient of US9928864. Therefore, it is unlikely to anticipate Claim 1 or its dependent claims.

3. US Pat. No. 6,383,668 (U.S. Pat. No. 6,383,668 B1)

• Full Citation: US6383668B1 - Magnetic recording media with antiferromagnetically coupled host layer for the magnetic recording layer
• Publication/Filing Date: Priority date: 2000-03-27; Publication date: 2002-05-07.
• Brief Description: This patent "addressed the thermal instability problem by replacing the conventional single magnetic recording layer... [with] a ferromagnetic layer that is coupled to a synthetic antiferromagnet". This also aimed to reduce the demagnetizing field in longitudinal magnetic recording.
• Potential Anticipation: Similar to US6280813B1, this patent proposes antiferromagnetic coupling or a synthetic antiferromagnet, which is distinct from the specific exchange spring structure with a gradient anisotropy nucleation host of US9928864. It does not disclose the nucleation host having increasing anisotropy from layer to layer, nor its relative position. Thus, it is unlikely to anticipate Claim 1 or its dependent claims.

4. US Pat. No. 6,468,670 (U.S. Pat. No. 6,468,670 B1)

• Full Citation: US6468670B1 - Magnetic recording disk with composite perpendicular recording layer
• Publication/Filing Date: Priority date: 2000-01-19; Publication date: 2002-10-22.
• Brief Description: In this patent, "a continuous ferromagnetic overlayer was introduced to increase the Signal to Noise Ratio (SNR)."
• Potential Anticipation: This patent describes a continuous ferromagnetic overlayer for SNR improvement. While it involves multiple magnetic layers, the description in US9928864 does not indicate that US6468670 discloses a nucleation host with increasing anisotropy constant K from layer to layer formed on a hard magnetic storage layer to enable domain wall assisted switching as claimed in US9928864. Therefore, it is unlikely to anticipate Claim 1 or its dependent claims.

5. US Pat. No. 5,851,643 (U.S. Pat. No. 5,851,643 A)

• Full Citation: US5851643A - Magnetic recording media and magnetic recording read-back system which uses such media
• Publication/Filing Date: Priority date: 1993-11-11; Publication date: 1998-12-22.
• Brief Description: The abstract of US5851643A describes a perpendicular magnetic recording medium having a soft magnetic layer, a non-magnetic intermediate layer, and a perpendicular magnetic recording layer, where the perpendicular recording layer has an inverse or inverse-reversed magnetic domain. This patent generally relates to perpendicular magnetic recording media.
• Potential Anticipation: While broadly related to perpendicular magnetic recording, US5851643A does not specifically disclose the "exchange coupled magnetic multilayer structure" of US9928864, particularly the key feature of a nucleation host with an increasing anisotropy gradient formed on the hard magnetic storage layer. Without these specific structural and material characteristics, it would not anticipate Claim 1 of US9928864.

6. US 2001/0051287 A1 (U.S. Pat. No. 2001/0051287 A1)

• Full Citation: US20010051287A1 - Magnetic recording medium and magnetic recording apparatus
• Publication/Filing Date: Priority date: 2000-06-12; Publication date: 2001-12-13.
• Brief Description: The abstract of US2001/0051287A1 describes a perpendicular magnetic recording medium with a perpendicular magnetic recording layer having multiple magnetic layers (e.g., hard magnetic layers and soft magnetic layers) stacked to improve thermal stability. It may include an intermediate non-magnetic layer or be directly coupled.
• Potential Anticipation: This reference describes multi-layered perpendicular media with hard and soft magnetic layers for thermal stability. This is a closer match in terms of general concept. However, Claim 1 of US9928864 specifies a nucleation host on the hard layer, and critically, this nucleation host has increasing anisotropy constant K from layer to layer. The general disclosure of hard/soft stacks in US2001/0051287A1 might provide a basis for some elements, but it does not explicitly disclose the specific anisotropy gradient within the nucleation host or the particular layer order (nucleation host on hard layer) with the specified function of the nucleation host as defined in Claim 1 of US9928864. Further examination of the detailed description of US2001/0051287A1 would be needed to definitively rule out anticipation, but based on the provided abstract-level information, it is unlikely to fully anticipate Claim 1.

7. US 2004/0191576 A1 (U.S. Pat. No. 2004/0191576 A1)

• Full Citation: US20040191576A1 - Magnetic recording medium, method manufacture therefor, and apparatus for magnetic reproducing and reproducing recordings
• Publication/Filing Date: Priority date: 2001-02-28; Publication date: 2004-09-30.
• Brief Description: The abstract of US2004/0191576A1 describes a perpendicular magnetic recording medium with a recording layer formed by stacking first and second magnetic layers. The second magnetic layer has a larger coercive force than the first. It mentions improving thermal stability and signal-to-noise ratio.
• Potential Anticipation: This patent describes a stacked magnetic layer system with differing coercive forces, where the harder layer is second. This could potentially relate to a hard magnetic storage layer and a softer layer. However, it does not explicitly disclose the specific "nucleation host" functionality, its placement on the hard layer, and particularly the increasing anisotropy constant K from layer to layer within the nucleation host, as required by Claim 1 of US9928864. Therefore, it is unlikely to anticipate Claim 1.

8. US 2005/0058855 A1 (U.S. Pat. No. 2005/0058855 A1)

• Full Citation: US20050058855A1 - Anti-ferromagnetically coupled perpendicular magnetic recording media with oxide
• Publication/Filing Date: Priority date: 2001-11-30; Publication date: 2005-03-17.
• Brief Description: The abstract of US2005/0058855A1 describes antiferromagnetically coupled (AFC) perpendicular recording media, including magnetic layers, a non-magnetic coupling layer, and at least one oxide. The purpose is to reduce grain size and improve SNR.
• Potential Anticipation: This patent focuses on AFC media with oxides. The coupling mechanism (antiferromagnetic) and the use of oxides for grain size reduction are different from the primary claims of US9928864, which emphasize exchange coupling and an anisotropy gradient in the nucleation host. Thus, it is unlikely to anticipate Claim 1.

9. US 2004/0053078 A1 (U.S. Pat. No. 2004/0053078 A1)

• Full Citation: US20040053078A1 - Magnetic recording medium and magnetic recording/reproducing apparatus
• Publication/Filing Date: Priority date: 2002-06-28; Publication date: 2004-03-18.
• Brief Description: The abstract of US2004/0053078A1 describes a perpendicular magnetic recording medium with a soft magnetic layer, an intermediate layer, and a perpendicular magnetic recording layer. The recording layer is formed of a plurality of magnetic sub-layers.
• Potential Anticipation: This patent discloses a perpendicular medium with a recording layer having multiple magnetic sub-layers. This is a very general description. It lacks the specific details of the "nucleation host with increasing anisotropy constant K from layer to layer" formed on the hard magnetic storage layer, which is central to Claim 1 of US9928864. Therefore, it is unlikely to anticipate Claim 1.

10. US 2004/0057156 A1 (U.S. Pat. No. 2004/0057156 A1)

• Full Citation: US20040057156A1 - Perpendicular magnetic recording media
• Publication/Filing Date: Priority date: 2002-09-19; Publication date: 2004-03-25.
• Brief Description: The abstract of US2004/0057156A1 describes a perpendicular magnetic recording medium with a soft magnetic layer and a magnetic recording layer on it. The magnetic recording layer can be a stacked structure of multiple magnetic layers.
• Potential Anticipation: Similar to US2004/0053078A1, this patent generally describes stacked magnetic layers in a perpendicular recording medium. Without specific disclosure of the anisotropic gradient within a nucleation host placed on a hard magnetic storage layer, as detailed in Claim 1 of US9928864, this patent would not anticipate the claims of US9928864.

11. US Pat. No. 7,550,210 (U.S. Pat. No. 7,550,210 B2)

• Full Citation: US7550210B2 - Perpendicular magnetic recording medium with multiple exchange-coupled magnetic layers having substantially similar anisotropy fields
• Publication/Filing Date: Priority date: 2006-03-09; Publication date: 2009-06-23.
• Brief Description: The abstract of US7550210B2 describes a perpendicular magnetic recording medium with multiple exchange-coupled magnetic layers, where the magnetic layers have substantially similar anisotropy fields. This is explicitly contrasted with the varying anisotropy of the present invention.
• Potential Anticipation: This patent explicitly states that its layers have "substantially similar anisotropy fields," which directly contradicts the key feature of US9928864's Claim 1, which requires the nucleation host to have "increasing anisotropy constant K from layer to layer." Therefore, this patent does not anticipate Claim 1 or any claims relying on the anisotropy gradient.

12. US 2007/0292720 A1 (U.S. Pat. No. 2007/0292720 A1)

• Full Citation: US20070292720A1 - Multilayer Exchange Spring Recording Media
• Publication/Filing Date: Priority date: 2006-06-17; Publication date: 2007-12-20.
• Brief Description: This is a publication within the same patent family as US9928864B2, having the same priority date and a very similar title and subject matter. It is an earlier publication of the same invention.
• Potential Anticipation: As this is an earlier publication of the same invention by the same inventor and assignee (originally), and shares the same priority date, it is not considered prior art under 35 U.S.C. § 102 against US9928864B2. It belongs to the same patent family.

Summary of Anticipation

Based on the analysis, the distinguishing feature of Claim 1 of US9928864, namely a nucleation host formed on the hard magnetic storage layer and comprising ferromagnetic layers with increasing anisotropy constant K from layer to layer, does not appear to be explicitly disclosed in any of the cited prior art patents. While some references discuss multilayer magnetic recording media and address thermal stability, none appear to combine the specific layer ordering and the precise anisotropy gradient within the nucleation host as claimed in US9928864. Therefore, it is unlikely that any of the listed prior art patents fully anticipate Claim 1 of US9928864. Claims dependent on Claim 1 would likewise not be anticipated by these references.