IP Law Daily, PATENT—Fed. Cir.: New trial ordered in magnetic thin-film developer’s infringement lawsuit against Seagate, (Sep 18, 2025)

By Saurabh Kashyap, B.A., M.A., LL.B., LL.M.

Jury’s non-infringement verdict vacated as district court prejudicially misconstrued a key claim term in the asserted patent, leading to a new trial on both infringement and enablement.

In a non-precedential opinion, the U.S. Court of Appeals for the Federal Circuit ordered a new trial in an infringement suit brought by a magnetic thin-film developer against Seagate Technology. The appellate court vacated a jury’s verdict of non-infringement and dismissed Seagate’s cross-appeal as procedurally improper. The panel held that the district court committed a prejudicial error by misconstruing the claim term “uniaxial symmetry broken structure” in the asserted thin-film magnetic materials patent, an error that undermined the fairness of the trial. Because the corrected claim construction could alter both the infringement analysis and the scope of the enablement inquiry, the case was remanded for a new trial on both issues (Lambeth Magnetic Structures, LLC v. Seagate Technology (US) Holdings Inc., No. 23-1335, 23-1346 (Fed. Cir. Sept. 17, 2025)).

Background. The plaintiff/appellant, Lambeth Magnetic Structures, LLC (LMS), is a company formed to commercialize magnetic thin-film innovations developed by Dr. David Lambeth, a pioneer in magnetic recording technology. LMS alleged that the defendant/ cross-appellant Seagate Technology (US) Holdings Inc. and Seagate Technology, LLC (together, Seagate), multinational leaders in hard disk drives, incorporated LMS’s patented thin-film magnetic structures into their products.

The asserted patent, U.S. Patent No. 7,128,988 (the ’988 patent), titled Thin Film Magnetic Structure, Magnetic Devices, and Method of Producing the Same, claims a crystalline thin-film material used in magnetic recording heads. Independent claim 1 recites a magnetic structure with a bcc-d layer forming a “uniaxial symmetry broken structure” on a hexagonal atomic template. The patent discloses that such arrangements provide higher magnetization and reduce noise by allowing recording heads to return to a non-interfering orientation after writing data. LMS asserted claims 1, 3, 6, 7, 9, 17, 19, and 27–29 against Seagate.

LMS filed suit in 2016 in the Western District of Pennsylvania. The district court’s 2017 Markman order construed the critical term “uniaxial symmetry broken structure” as “a structure that is uniaxial as a result of the structure being symmetry broken.” Both sides moved for summary judgment in 2018, but the court found genuine disputes of fact and denied the motions.

A jury trial in April 2022 resulted in a verdict of non-infringement and no invalidity. The district court denied the parties’ post-trial motions for judgment as a matter of law (JMOL) and for a new trial. LMS appealed the non-infringement ruling, while Seagate cross-appealed, arguing the patent lacked enablement under 35 U.S.C. § 112.

Claim construction. On appeal, LMS challenged the district court’s addition of a causal link between symmetry breaking and uniaxiality. The Federal Circuit reviewed claim construction de novo, emphasizing that claim terms are generally given their ordinary and customary meaning to a skilled artisan at the time of invention (Phillips v. AWH Corp., 415 F.3d 1303, 1312–13 (Fed. Cir. 2005) (en banc)). Referencing Abbott Lab’ys v. Syntron Bioresearch, Inc., 334 F.3d 1343, 1352 (Fed. Cir. 2003), the appellate court found no waiver, distinguishing LMS’s reliance on the district court’s construction in expert reports and pretrial statements from an actual concession.

Further, the court held that "uniaxial" and "symmetry broken" each described structural properties, not functional causation. Importing a functional requirement from the specification into the claims was found improper under Toro Co. v. White Consol. Indus., Inc., 266 F.3d 1367, 1371 (Fed. Cir. 2001). It rejected Seagate’s argument that grammar required causation, noting that adjectives without a conjunction are presumed independent (In re Hyatt, 708 F.2d 712, 714 (Fed. Cir. 1983)).

Seagate further argued that the term was a “coined term” with no meaning outside the patent, invoking Honeywell Int’l Inc. v. Universal Avionics Sys. Corp., 488 F.3d 982, 991 (Fed. Cir. 2007). The Federal Circuit acknowledged its recent decision in Malvern Panalytical Inc. v. TA Instruments-Waters LLC, 85 F.4th 1365, 1374 (Fed. Cir. 2023), which permitted consideration of coined terms within a patent context but cautioned against unduly narrowing them. Here, the ordinary meaning within the patent supported LMS's construction: "a symmetry broken structure that is uniaxial."

Harmless error. Seagate argued that even if the district court erred, the error was harmless because the jury would have found no infringement regardless. The court disagreed. Because the general verdict did not specify its grounds, it was impossible to conclude that the misconstruction was irrelevant. Citing Teleflex, Inc. v. Ficosa N. Am. Corp., 299 F.3d 1313, 1328 (Fed. Cir. 2002), the Federal Circuit emphasized that an erroneous jury instruction on claim construction cannot be deemed harmless absent certainty that correction would not alter the result. Moreover, Seagate explicitly relied on the “as a result” requirement in its trial arguments, rendering the error prejudicial (Network-1 Techs., Inc. v. Hewlett-Packard Co., 981 F.3d 1015, 1025 (Fed. Cir. 2020)).

Enablement and the cross-appeal. Seagate’s cross-appeal sought reversal on enablement grounds, arguing that no reasonable jury could have found the ’988 patent enabled. Citing Therasense, Inc. v. Becton, Dickinson & Co., 593 F.3d 1325, 1337 (Fed. Cir. 2010) and Bailey v. Dart Container Corp. of Mich., 292 F.3d 1360, 1362 (Fed. Cir. 2002), the Federal Circuit dismissed the cross-appeal, holding that a prevailing party may not cross-appeal merely to press alternative grounds for affirmance. Because Seagate asserted invalidity only as a defense, not as a counterclaim, its appeal resembled those dismissed in AntennaSys, Inc. v. AQYR Techs., Inc., 976 F.3d 1374, 1377 n.1 (Fed. Cir. 2020).

Nevertheless, the appellate court considered Seagate’s enablement arguments as alternative grounds under Praxair, Inc. v. ATMI, Inc., 543 F.3d 1306, 1322 (Fed. Cir. 2008).

New trial on enablement. The court held that the corrected construction broadened the claim scope, thereby altering the enablement analysis. It exercised its discretion, guided by Witco Chem. Corp. v. Peachtree Doors, Inc., 787 F.2d 1545, 1548 (Fed. Cir. 1986), and Eaton Corp. v. Rockwell Int’l Corp., 323 F.3d 1332, 1344 (Fed. Cir. 2003), to order a new trial on enablement. The Federal Circuit reasoned that because infringement and validity were intertwined, both issues should be retried together.

Conclusion. Thus, the Federal Circuit vacated the district court’s non-infringement judgment, dismissed Seagate’s cross-appeal, and remanded for a new trial on infringement and enablement under the corrected construction of “uniaxial symmetry broken structure.”

The Case is Nos. 23-1335, 23-1346.

Judge: Reyna, J.

Attorneys: Jeffrey A. Lamken (MoloLamken LLP) for Lambeth Magnetic Structures, LLC. Chad Drown (Faegre Drinker Biddle & Reath LLP) for Seagate Technology [US]Holdings Inc. and Seagate Technology LLC.

Companies: Lambeth Magnetic Structures, LLC; Seagate Technology (US) Holdings Inc.; Seagate Technology LLC

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