Dual-functional magnetic glues for quantum packaging

As quantum and superconducting devices get smaller, conventional magnetic bulk shields fail to protect adjacent components from each other’s stray magnetic fields. Irregular microscopic surfaces between components also create air voids with low magnetic permeability, further disrupting shielding.

To prevent leaky magnetic flux from seeping into sensitive chip components, Barani et al. developed a composite soft-magnetic interface material (MIM). Made of dispersed nanoparticles of soft ferromagnetic Mu-metal fillers in a cryogenically stable epoxy, the MIM fills interfacial gaps within a chip and completes the magnetic circuit.

“We aimed to integrate both magnetic and thermal compatibility into a scalable solution for advanced quantum and cryogenic packaging architectures,” said author Zahra Barani.

The MIM has high magnetic permeability across a wide cryogenic temperature range, making it suitable under typical quantum device operating conditions. When layered between magnetic shield caps and the chip surface, magnetic field lines flow through it, instead of through sensitive components. Because it loses magnetization in the absence of external fields, the material does not perturb devices with residual fields.

Adjusting the nanoparticle fillers tunes the material’s coefficient of thermal expansion (CTE) to match the magnetic cap and substrate. Decreasing CTE mismatch minimizes thermal stress and mechanical failure during cryogenic cycling, making devices more cryogenically stable.

“In the broader context, these materials could provide a practical route toward localized, cryo-compatible magnetic shielding solutions that reduce residual magnetic noise and improve coherence in next-generation superconducting quantum devices,” said author Mark Adams.

Moving forward, the team intends to refine the MIM microstructure and investigate how its particle alignment and interface geometry impact permeability in low magnetic fields. Eventually, they aim to evaluate the MIM’s performance in operational quantum hardware.

Source: “Dual-functional soft magnetic interface materials for quantum packaging,” by Zahra Barani, Harshil Goyal, Chase C. Tillman, Oluchi Onwuvuche, Jacob Ward, and Mark L. Adams, Applied Physics Letters (2025). The article can be accessed at https://doi.org/10.1063/5.0294328 .