R&D: Effect of N2 Addition on Nanostructure and Magnetic Properties of Sputtered FePt-BN Granular Films During Deposition for HAMR
Magnetic properties and nanostructure for FePt-30vol%BN granular films deposited while flowing N2 gas with ratio between 0 and 5% with respect to total flow of N2 + Ar investigated
This is a Press Release edited by StorageNewsletter.com on April 7, 2022 at 2:00 pmIEEE Transactions on Magnetics has published an article written by Kim Kong Tham, Tanaka Kikinzoku Kogyo K.K., Tsukuba 300-4247, Japan, Takashi Saito, Department of Electronic Engineering, Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan and Research assistant, Graduate Program in Spintronics (GP-Spin), Tohoku University, Sendai 980-8578, Japan, Ryosuke Kushibiki, Tanaka Kikinzoku Kogyo K.K., Tsukuba 300-4247, Japan, and Shin Saito, Department of Electronic Engineering, Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan.
Abstract: “Magnetic properties and nanostructure for FePt-30vol%BN granular films deposited while flowing N2 gas with ratio between 0 and 5% with respect to the total flow of N2 + Ar are investigated. Here is the list of the results. (1) A maximum coercivity (Hc) of 18.9 kOe, a saturation magnetization (Ms) of 600 emu/cm3, a perpendicular magnetic anisotropy (Ku⊥) of 1.7×107 erg/cm3, and a magnetic anisotropy field (Hk) of 58 kOe, with smaller grain size and higher degree of grain separation are obtained when N2 gas with a ratio of around 2% is added. (2) Higher fraction of N2 gas ratio leads to an increase of the amount of magnetic grains with c-axis parallel to the film plane. (3) Lattice constant ? remains constant, a minimum value of lattice constant c and the ratio c/? are also observed for a N2 ratio of around 2%. (4) There are two phenomena observed in nanostructure and magnetic properties defined by the N2 ratio. For N2 ratios under 2%, changes in the c/? ratio, the degree of order, and the agglomeration suppression of grains enhance Ms, Ku⊥ and Hk. This indicates that the segregation of B into grain boundaries as the result of the N2 addition. For N2 ratios over 2%, the change of tetragonal into cubic FePt magnetic grains, the reduction of the degree of order, and the decrease of Ms and Ku⊥ suggest that excess nitrogen dissolves into the FePt magnetic grains. (5) Another consequence of the 2% N2 ratio is the enhancement of the magnetic grain decoupling along with the increase of Hk, this results in the maximization of Hc.“
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