R&D: Anisotropic Exchange Spin Model to Investigate Curie Temperature Dispersion of L10-FePt Magnetic Nanoparticles
Research highlights the role of exchange anisotropy in amplifying finite-size effects and underscores importance of size control in HAMR media.
This is a Press Release edited by StorageNewsletter.com on June 6, 2025 at 2:00 pmJournal of Applied Physics has published an article written by Kohei Ochiai, Tomoyuki Tsuyama, Sumera Shimizu, Resonac Corporation, Research Center for Computational Science and Informatics, 8 Ebisu-cho, Kanagawa-ku, Yokohama, Kanagawa 221-8517, Japan, Lei Zhang, Jin Watanabe, Fumito Kudo, Resonac Hard Disk Corporation, Research & Development Center, 5-1, Yawatakaigan-dori, Ichihara, Chiba 290-0067, Japan, Jian-Gang Zhu, Data Storage Systems Center, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA, Electrical and Computer Engineering Department, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA, and Materials Science and Engineering Department, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA, and Yoshishige Okuno, Resonac Corporation, Research Center for Computational Science and Informatics, 8 Ebisu-cho, Kanagawa-ku, Yokohama, Kanagawa 221-8517, Japan.
Abstract: “We developed an anisotropic exchange spin model that accounts for magnetic anisotropy and evaluated the Curie temperature ( T c) dispersion due to finite-size effects in L1 0-FePt nanoparticles. In heat-assisted magnetic recording (HAMR) media, a next-generation magnetic recording technology, high-density recording is achieved by locally heating L1 0-FePt nanoparticles near their T c and rapidly cooling them. However, variations in T c caused by differences in particle size and shape can compromise recording stability and areal density capacity, making the control of T c dispersion critical. In this study, we constructed atomistic Landau–Lifshitz–Gilbert models to explicitly incorporate the spin exchange anisotropy of L 1 0-FePt, based on parameters determined by first-principles calculations. Using this model, we evaluated the impact of particle size on T c dispersion. As a result, (1) the T c dispersion critical to the performance of HAMR can be reproduced, whereas it was previously underestimated by isotropic models and (2) approximately 70 % of the experimentally observed T c dispersion can be attributed to particle-size effects. This research highlights the role of exchange anisotropy in amplifying finite-size effects and underscores the importance of size control in HAMR media.“
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