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VIDEO DOI: https://doi.org/10.48448/s083-5005

technical paper

MMM 2022

November 07, 2022

Minneapolis, United States

FePt BN Granular HAMR Media with High Grain Aspect Ratio and High L10 Ordering on Corning Lotus™ NXT Glass

The key to realizing high area recording density capability (ADC) for heat assisted magnetic recording (HAMR) is to achieve small grain size (and pitch) in the granular L10 FePt media with a sufficiently high grain aspect ratio 1. Media such as FePt-C, FePt-SiOx, and FePt-TaOx, or multilayers made of a combination of them, appear not able to reach the desired goal because of their failure to achieve either high grain aspect ratio, small grain size, or high L10 ordering, respectively 2, 3.
In this study, using the co-sputtering technique, we demonstrate the fabrication of FePt-BN granular media with much reduced FePt grain size and high grain aspect ratio. In particular, an underlayer stack of Ta(5nm)/Cr(50)/MgO(9) is first deposited on Corning LotusTM NXT glass followed by co-sputtering of FePt and BN at an elevated substrate temperature along. A RF bias is applied to the substrate during the FePt-BN deposition with a short and optimized delay. Figure 1C shows the order parameter as a function of substrate temperature for the FePt-BN granular film media, calculated from XRD measurements. The volumetric concentration of BN is at 38%. Figure 1A on the left of the figure shows a cross-section TEM micrograph of the FePt-BN layer formed at a substrate temperature of 725 oC. Figure 1B shows a cross-section TEM picture of FePt-BN/FePt-SiOx multilayer granular film with temperature and composition graded over the grain height for producing tall grains 4 for comparison. The grain size of single layer FePt-BN film (Figure1 A) is around 4 nm with an aspect ratio of 2 while the grain size of the FePt-BN/FePt-SiOx multilayer film is around 7nm and grain height 11nm. The small grain size with a relatively high grain aspect ratio in the single layer FePt-BN film is promising for enabling high area recording density capability.
1Y. Kubota et al., “Heat-Assisted Magnetic Recording’s Extensibility to High Linear and Areal Density,” IEEE Transactions on Magnetics, vol. 54, no. 11, Nov. 2018.
2 A. Perumal, Y.K. Takahashi, K. Hono, “L10 FePt-C Nanogranular Perpendicular Anisotropy Films with Narrow Size Distribution”, Appl. Phys. Express 1 101301 (2008).
3 B. S. D. C. S. Varaprasad, M Chen, YK Takahashi, K Hono “L1-Ordered FePt-Based Perpendicular Magnetic Recording Media for Heat-Assisted Magnetic Recording” IEEE transactions on magnetics 49 (2), 718-722 (2013)
4 C. Xu, B. Zhou, T. Du, B.S.D.C.S. Varaprasad, D.E. Laughlin, J.-G. Zhu, Understanding the growth of high-aspect-ratio grains in granular L10-FePt thin-film magnetic media, APL Materials. 10 (2022).

Figure 1 (A) Out of plane micrographs of FePt-BN (8 nm) (B) Out of plane micrographs of FePt-BN/FePt-SiO 2 (11 nm) and (C) Order parameter Vs set temperature of FePt-BN sample


Transcript English (automatic)

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