R&D: Four Articles on HAMR, MAMR and SMR Disks

R&D: High-throughput SEM imaging of nanoscale metal grains for heat assisted magnetic recording
High-throughput SEM grain imaging as demonstrated in this work yields large materials characterization datasets without expensive detectors or specialized hardware.

AIP Advances has published, in special collection: 70th Annual Conference on Magnetism and Magnetic Materials, an article written by Matthew R. Hauwiller, Charles Mann, Peter Mach, Tong Zhao, Tuo Gao, Abdurahman D. Abdurahman, Stephanie Hernandez, Karen Terry, Brent Voigt, and Michael C. Kautzky, Seagate Technology, Bloomington, Minnesota 55435, USA.

Abstract: “Development of nanoscale magnetic and plasmonic materials for applications such as Heat Assisted Magnetic Recording requires precise control and understanding of the materials’ microstructure. Scanning Electron Microscopy (SEM) has the speed and resolution to characterize grain structure with high throughput, but there is little precedence for imaging sub-50 nm, crystallographically-aligned metal grains in a traditional SEM without specialized detectors or optics. Imaging ungrounded micron-scale metal structures on wafers presents further challenges due to charging. By optimizing imaging parameters for each sample, sub-50 nm and sub-25 nm metal grains were captured. Monte Carlo simulations were used to understand the depth of backscattered electron signal for the stacks of materials and the effect of grain boundary tilt on grain boundary contrast. High-throughput SEM grain imaging as demonstrated in this work yields large materials characterization datasets without expensive detectors or specialized hardware. Translating the qualitative SEM grain images to quantitative characterization requires continued algorithm development, yet there are significant opportunities for automated materials development and structure–property elucidation for SEM grain imaging combined with computer vision. The present and future of magnetic devices requires nanoscale materials control, and high-throughput SEM grain imaging is a promising metrology route for understanding and producing those structures.“

R&D: Quantifying erasure and interference from adjacent tracks in heat-assisted magnetic recording
Measurements from two medium designs show such significant difference in adjacent track erasure that the ranking of their areal density capability is impacted.

AIP Advances has published, in special collection: 70th Annual Conference on Magnetism and Magnetic Materials, an article written by Xuan Zheng, Walter R. Eppler, Jay Loven, and Jason Gadbois, Advanced Transducer Development, Seagate Technology, Bloomington, Minnesota 55435, USA

Abstract: “With track spacing in heat-assisted magnetic recording approaching the width of the reader and the thermal spot, the areal density capability is significantly penalized by interference and erasure from adjacent tracks. To quantify the impact, spin stand tests have been developed based on synchronous writing to capture the noise-free waveforms of the adjacent tracks and the partially erased data track, respectively. The results show that side reading interference from foreground adjacent tracks varies from 13 to 18 dB and strongly correlates with the effective reader width. Adjacent track erasure dominates at the edge of the data track, reduces its signal and increase its spatial noise. The signal loss and spatial noise increase scale with logarithm of the number of adjacent track writes. Measurements from two medium designs show such significant difference in adjacent track erasure that the ranking of their areal density capability is impacted.“

R&D: Cubic anisotropy media for microwave assisted magnetic recording
Microwave-assisted magnetic recording using media containing cubic anisotropy materials was investigated.

AIP Advances has published, in special collection: 70th Annual Conference on Magnetism and Magnetic Materials, an article written by Simon John Greaves, RIEC, Tohoku University, Katahira 2-1-1, Aoba ku, Sendai 980-8577, Japan, and Yasushi Kanai, Niigata Institute of Technology, Kashiwazaki 945-1195, Japan.

Abstract: “Microwave-assisted magnetic recording using media containing cubic anisotropy materials was investigated. A comparison of grains with either uniaxial or cubic anisotropy showed larger coercivity reductions could be obtained when using cubic anisotropy grains. Composite recording media consisting of a hard layer with cubic anisotropy and a soft layer with uniaxial anisotropy gave higher SNR than composite media in which the hard and soft layers both had uniaxial anisotropy. One possible drawback was the lower energy barrier of media containing cubic anisotropy material.“

R&D: Mitigating the Write-amplification effect of large-scale semi-external graphs on SMR drives
Paper introduces innovative methodologies to enhance the performance of disk-based graph processing systems, specifically addressing the write amplification issue in SMR disks.

ACM Digital Library has published, in RACS ’25: Proceedings of the International Conference on Research in Adaptive and Convergent Systems, an article written by Yi-Syuan Lin, National Tsing Hua University, Hsinchu, Taiwan, Qi-Cheng Wu, National Chung Cheng University, Chiayi, Taiwan, Chih-Xuan Shen, National Tsing Hua University, Hsinchu, Taiwan, Yu-Pei Liang, National Chung Cheng University, Chiayi, Taiwan, Wei-Kuan Shih, National Tsing Hua University, Hsinchu, Taiwan, and Yuan-Hao Chang, National Taiwan University, Taipei, Taiwan.

Abstract: “With the advancement of technology, the complexity and size of graph data have expanded significantly. Shingled Magnetic Recording (SMR) is an ideal choice for handling large-sized data due to its high storage capacity. However, SMR faces challenges with write amplification during data updates. This paper introduces innovative methodologies to enhance the performance of disk-based graph processing systems, specifically addressing the write amplification issue in SMR disks. We propose the Adaptive SMR Update Strategy (ASUS), coupled with Layout Reorganizer, to decide between in-place updates and out-place updates intelligently. Finally, the experimental evaluations demonstrate that ASUS achieves a write amplification reduction of up to 58%.“