VP8-04 Magnetization Transition in Dual-Layer Heat-Assisted Magnetic Recording
Creators: Yugen Jian
Vitaliy Lomakin
Ke Luo
and Jincai Chen
Publisher: name: IEEE
Year: 2025

Three-dimensional magnetic recording (3DMR) has recently been introduced as a novel solution that promises to far exceed the capacity of existing hard disk drive (HDD) products [1,2]. The multi-layer recording medium of 3DMR presents various new challenges, one of which will be more complex magnetization transitions. In this work, the magnetization transitions and their associated noise in a dual-layer heat-assisted magnetic recording (HAMR) system are investigated and discussed via micromagnetic simulation. Dual-layer FePt-based nanogranular films [3] are modeled and the two-pass writing process under HAMR is simulated by solving the Landau-Lifshitz-Bloch (LLB) equation on MARS [4]. At the first pass, both layers are heated beyond their Curie temperatures. Their magnetization polarities are all aligned with the direction of the applied field. At the second pass, the peak temperature of the thermal field is higher than the Curie temperature of the top layer but lower than that of the bottom layer. Only the magnetization state of the top layer will be changed. Fig. 1 shows the variation of each layer’s magnetization distribution between the two passes when writing the transition pattern that is denoted as [01,10] (in terms of adjacent bit-pairs [Bxtop Bxbottom, Bytop Bybottom]). The medium signal-to-noise ratio (SNR) is calculated from the obtained magnetization of 6 possible transition patterns, as shown in Fig. 2. The results indicate that, in addition to grain distribution and thermal fluctuation, the final SNR seems to depend on the number of times and the sequence in which the magnetization states are switched during the two-pass writing, explaining why the opposite transitions in the dual layers bring the most severe noise.References: [1] E. Roddick, M. Kief, and A. Takeo, in 2022 IEEE 33rd Magnetic Recording Conference (TMRC), pp. 1–2 (2022). [2] S. Greaves, J. Magn. Magn. Mater., vol. 588, p. 171343 (2023). [3] P. Tozman, S. Isogami, I. Suzuki et al, Acta Mater., vol. 271, p. 119869 (2024). [4] S.E. Rannala, A. Meo, S. Ruta et al, Comput. Phys. Commun., vol. 279, p. 108462 (2022).
Three-dimensional magnetic recording (3DMR) has recently been introduced as a novel solution that promises to far exceed the capacity of existing hard disk drive (HDD) products [1,2]. The multi-layer recording medium of 3DMR presents various new challenges, one of which will be more complex magnetization transitions. In this work, the magnetization transitions and their associated noise in a dual-layer heat-assisted magnetic recording (HAMR) system are investigated and discussed via micromagnetic simulation. Dual-layer FePt-based nanogranular films [3] are modeled and the two-pass writing process under HAMR is simulated by solving the Landau-Lifshitz-Bloch (LLB) equation on MARS [4]. At the first pass, both layers are heated beyond their Curie temperatures. Their magnetization polarities are all aligned with the direction of the applied field. At the second pass, the peak temperature of the thermal field is higher than the Curie temperature of the top layer but lower than that of the bottom layer. Only the magnetization state of the top layer will be changed. Fig. 1 shows the variation of each layer’s magnetization distribution between the two passes when writing the transition pattern that is denoted as [01,10] (in terms of adjacent bit-pairs [Bxtop Bxbottom, Bytop Bybottom]). The medium signal-to-noise ratio (SNR) is calculated from the obtained magnetization of 6 possible transition patterns, as shown in Fig. 2. The results indicate that, in addition to grain distribution and thermal fluctuation, the final SNR seems to depend on the number of times and the sequence in which the magnetization states are switched during the two-pass writing, explaining why the opposite transitions in the dual layers bring the most severe noise.References: [1] E. Roddick, M. Kief, and A. Takeo, in 2022 IEEE 33rd Magnetic Recording Conference (TMRC), pp. 1–2 (2022). [2] S. Greaves, J. Magn. Magn. Mater., vol. 588, p. 171343 (2023). [3] P. Tozman, S. Isogami, I. Suzuki et al, Acta Mater., vol. 271, p. 119869 (2024). [4] S.E. Rannala, A. Meo, S. Ruta et al, Comput. Phys. Commun., vol. 279, p. 108462 (2022).