PTAB

IPR2026-00015

Resonac Hard Disk Corp v. Mr Technologies GmbH

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Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Magnetic Recording Media
  • Brief Description: The ’997 patent describes a perpendicular magnetic recording (PMR) medium designed to overcome the trade-off between thermal stability and writeability. The invention purports to achieve this by using a multi-layer "nucleation host" with graded magnetic anisotropy, positioned on top of a hard magnetic storage layer, to reduce the coercive field required for writing data without compromising data stability.

3. Grounds for Unpatentability

Ground 1: Obviousness over Takenoiri - Claims 1-2 and 5-7 are obvious over Takenoiri alone.

  • Prior Art Relied Upon: Takenoiri (Patent 8,329,321).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Takenoiri taught all elements of the challenged claims. Specifically, Takenoiri’s “first magnetic recording layer” was identified as the claimed “hard magnetic storage layer,” with petitioner citing data from Takenoiri’s examples to show it meets the coercive field requirement of >0.5 T. While Takenoiri’s primary embodiment was a bi-layer structure, it expressly taught extending this to “three or more magnetic recording layers.” Petitioner contended this explicit suggestion rendered a tri-layer structure obvious, wherein the additional softer magnetic layers (e.g., a second and third recording layer) constitute the claimed “nucleation host.” The petition further argued that Takenoiri’s disclosure of individual magnetization reversal demonstrated that the nucleation host’s coercive field (Hn) would be lower than the hard layer’s (Hs), as claimed. The final limitation of claim 1, an increasing anisotropy constant (K) in the nucleation host toward the hard layer, was argued to be an obvious modification to achieve Takenoiri’s stated goal of reducing the switching field while maintaining thermal stability.
    • Motivation to Combine: The motivation was not to combine distinct references, but to modify Takenoiri’s bi-layer structure as it explicitly suggested. A person of ordinary skill in the art (POSITA) would extend the structure to three or more layers to further improve the balance between writeability and thermal stability, which was a central problem addressed by Takenoiri. Configuring the layers with graded anisotropy and coercivity was a known design choice for achieving this goal.
    • Expectation of Success: A POSITA would have a reasonable expectation of success because Takenoiri taught how to tune the magnetic properties (coercivity and anisotropy) of each layer by adjusting material composition and thickness. Applying these known tuning methods to the suggested third layer to create a graded structure was presented as a predictable and straightforward design implementation.

Ground 2: Obviousness over Takenoiri and Li - Claims 4 and 9 are obvious over Takenoiri in view of Li.

  • Prior Art Relied Upon: Takenoiri (Patent 8,329,321) and Li (Patent 7,846,564).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground built upon Ground 1, addressing the additional limitation in dependent claims 4 and 9 requiring the nucleation host to comprise “grains with an average diameter greater than 2 nm and less than 10 nm.” Petitioner argued that while Takenoiri disclosed a granular structure for its recording layers, it did not specify a precise grain size. Li, however, was presented as analogous art that addressed the same technical problem and disclosed using similar CoCr-based magnetic materials with a grain size of about 4 to 10 nm to achieve high-density recording. Therefore, Li supplied the missing grain size limitation.
    • Motivation to Combine: A POSITA seeking to optimize the high-density recording medium taught by Takenoiri would have been motivated to consult analogous art like Li for specific microstructural parameters. Since both references aimed to improve performance in granular PMR media, incorporating Li's optimized grain size into Takenoiri's multi-layer structure was argued to be a logical step to enhance performance parameters like writability and signal-to-noise ratio, which are dependent on grain structure.
    • Expectation of Success: A POSITA would have a reasonable expectation of success in implementing Li's grain size in Takenoiri’s structure. Petitioner asserted that both references taught controlling grain size using conventional and well-understood fabrication techniques, making the combination a routine and predictable microstructural refinement rather than an inventive step.

4. Relief Requested

  • Petitioner requests the institution of an inter partes review and the cancellation of claims 1-2, 4-7, and 9 of the ’997 patent as unpatentable.