Matlak J, Rismaniyazdi E, Komvopoulos K
Department of Mechanical Engineering, University of California, Berkeley, CA, 94720, USA.
Western Digital Company, San Jose, CA, 95119, USA.
Sci Rep. 2018 Jun 28;8(1):9807. doi: 10.1038/s41598-018-27688-4.
The intense laser heating in heat-assisted magnetic recording (HAMR) has been a major hindrance to HAMR technology from becoming commercially viable. Thermal damage of the near-field transducer (NFT) and write pole (WP) embedded in the trailing edge of the magnetic head due to failure of the protective carbon overcoat after prolonged heating at an elevated temperature are major obstacles. Therefore, the main objective of this study was to develop an effective coating method for HAMR heads. This was accomplished by introducing a new class of layered coatings consisting of ultrathin amorphous carbon (a-C) overcoat, adhesion (SiN) layer, and buffer (NiCr or TaO) layer sequentially deposited onto Au and FeCo base layers to mimic the layer stacking of NFT and WP elements, respectively. The structural stability of the a-C overcoats and diffusion characteristics of each comprising layer under conditions of heating at 350 °C for 30 min in an Ar atmosphere were investigated by high-resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy (STEM), and electron energy loss spectroscopy (EELS). For most stacking configurations the HRTEM/STEM and EELS results generally revealed some layer intermixing and minute carbon atom rehybridization in the heated a-C overcoats. The findings of this investigation suggest that further optimization of the developed layered coatings can provide a viable solution to thermal damage of HAMR heads.
热辅助磁记录（HAMR）中强烈的激光加热一直是阻碍HAMR技术实现商业可行性的主要因素。由于在高温下长时间加热后，保护碳涂层失效，导致嵌入磁头后缘的近场换能器（NFT）和写入极（WP）受到热损伤，这是主要障碍。因此，本研究的主要目标是开发一种适用于HAMR磁头的有效涂层方法。通过引入一类新型的分层涂层来实现这一目标，该涂层由超薄非晶碳（a-C）外涂层、粘附（SiN）层和缓冲（NiCr或TaO）层依次沉积在Au和FeCo基层上，分别模拟NFT和WP元件的层堆叠结构。通过高分辨率透射电子显微镜（HRTEM）、扫描透射电子显微镜（STEM）和电子能量损失谱（EELS），研究了a-C外涂层在350 °C的氩气气氛中加热30 min条件下的结构稳定性以及各组成层的扩散特性。对于大多数堆叠结构，HRTEM/STEM和EELS结果通常显示，加热后的a-C外涂层存在一些层间混合和微小的碳原子重新杂化现象。本研究结果表明，对所开发的分层涂层进行进一步优化，可以为解决HAMR磁头的热损伤问题提供一个可行的方案。
