On Tuesday, May 5th 2026, we have the pleasure to welcome in SPINTEC Yukiko Takahashi from NIMS, Japan. She will give us a seminar at 09:00 entitled : Material development for HAMR and its prospects
Place : IRIG/SPINTEC, auditorium 445 CEA Building 10.05 (presential access to the conference room at CEA in Grenoble requires an entry authorization. Request it before April 2th at admin.spintec@cea.fr)
video conference : https://univ-grenoble-alpes-fr.zoom.us/j/98769867024?pwd=dXNnT3RMeThjYStybGVQSUN0TVdJdz09
Meeting ID: 987 6986 7024
Passcode: 025918
Abstract : With the rapid expansion of IoT and digital transformation, data centers demand ever-higher storage densities. Heat-assisted magnetic recording (HAMR) employs L1₀-FePt, whose magnetic anisotropy is an order of magnitude larger than that of conventional CoCrPt, enabling ultrahigh-density recording. Achieving areal densities beyond 4 Tbit/in² requires granular films with grain sizes ~4.3 nm and narrow inter-grain pitch with ~1 nm [1]. However, conventional segregant systems such as FePt-C and FePt-BN have not yet simultaneously satisfied the required microstructural and magnetic criteria.
To overcome this limitation, we introduced a data- driven materials design framework using the NIMS Research Data Express (RDE) platform. By collecting experimental datasets and applying machine learning to FePt-C and FePt-BN systems, we predicted sputtering conditions that led to FePt-BN-C granular films with sub-6 nm grain sizes and coercivities up to 3.7 T. Although iterative prediction cycles improved the microstructure to 4.9 nm grains, the results also clarified the intrinsic difficulty of meeting all 4 Tbit/in² requirements within this materials system alone.
Beyond materials optimization, three-dimensional magnetic recording offers an additional pathway toward higher areal density. As a proof of concept, FePt-C/Ru-C/FePt-C trilayers were fabricated, demonstrating epitaxial stacking and distinct magnetic switching behaviors arising from different ordering states in the upper and lower FePt layers [2]. Strategies to improve the structural and magnetic quality of the upper layer will be discussed.
[1] D. Weller et al., IEEE Trans. Magn. 50, 3100108 (2014).
[2] P. Tozman et al.,Acta Mater. 271, 119869 (2024).
Biography : Dr. Yukiko Takahashi received her Ph.D in Electrical Engineering from Tohoku University in 2001 and joined National Institute for Materials Science (NIMS). Her pioneering research is the development of FePt-C granular recording media for HAMR, demonstration of AOS and 3D-HAMR using FePt granular media. In addition to this, she actively works on the development of new permanent magnetic materials.
She has published more than 270 research papers and has strong research connections with HDD industries.
Currently, she is the director of Research Center for Magnetic and Spintronic Materials of NIMS and holds a concurrent professorship at the University of Tsukuba and Tohoku University.
