The 284th Special CMSM seminar

Effect of MgTiO/ Pt-BN/ MgTiO underlayer on FePt-X grain size and distributions

Varaprasad Bollapragada, Ajay Tiwari, Huaixun Huyan, Nan Tang, Iwao Okamoto, Ajan Antony, Mrugesh Desai, and Ram Acharya
Western Digital Corporation, San Jose, California, 95119, USA
Date & Time: 14:00 - 15:00, August 5th (Tue), 2025.
Place: 5F conference room, Advanced Structural Materials Buiding, Sengen.

Abstract:

The relentless growth of digital information is driving an unprecedented demand for high‐capacity data storage. To meet this challenge, recording media must achieve bit densities far beyond current technologies. One promising route is Heat Assisted Magnetic Recording (HAMR), which requires media with exceptionally high magnetic anisotropy (Ku) to maintain thermal stability when grain sizes shrink below 5 nm. L10‐ordered FePt stands out as an ideal candidate, offering a Ku on the order of 10^7 erg/cm³ and ensuring long‐term data retention at ultrahigh densities. In HAMR media, the granular FePt layer is deposited atop an underlayer that seeds its crystallographic orientation and controls grain growth. MgO‐based underlayers have emerged as critical enablers, promoting (001) texture, enhancing chemical ordering, and yielding well‐isolated FePt grains. By fine‐tuning the composition, thickness, and deposition conditions of the MgO underlayer, one can engineer the nucleation sites and grain boundary characteristics essential for minimizing magnetic interactions and optimizing write/read performance. Recent developments have highlighted the effectiveness of magnesium titanium oxide (MgTiO, MTO) and its nitrogen-doped variant (MgTiON, MTON) as underlayers for FePt-X magnetic media. These materials play a pivotal role in establishing the proper texture and granular architecture required for optimal magnetic performance. In this study, we investigate the influence of a tri-layer structure consisting of MgTiO/Pt-BN/MgTiO on the texture and microstructural evolution of FePt-X magnetic layers. Our analysis focuses on the interplay between layer interfaces and magnetic grain formation, offering insight into how engineered seed and underlayer compositions contribute to next-generation ultrahigh-density HDD technologies.

(Contact)

Hossein Sepehri Amin, Green Magnetic Materials Gr., CMSM

E-mail: H.SEPEHRIAMIN[at]nims.go.jp