Epitaxially Grown FCC/BCC/HCP Multi-Underlayers for High Performance Perpendicular Media

Abstract

In this study, a new underlayer structure consisting of FCC NiW, BCC Cr and HCP Ru layers is investigated as a promising underlayer that offers good perpendicular magnetic and recording properties. The FCC (111) planes of NiW layer enhances hetero-epitaxial growth of the subsequent BCC Cr (110), HCP Ru and Co (0002) layers in the direction perpendicular to the film plane. After the NiW-Cr-Ru layer structure is optimized, the Co (0002) <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</i> axis dispersion is greatly reduced and ~ 3 degree of XRD rocking width is achieved. As a result, excellent magnetic properties such as high coercivity, high nucleation field and narrow switching field distribution (SFD) are obtained. In addition, low media jitter and high signal-to-media noise (SNR <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</i> ) can be achieved. The SNR <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</i> is also highly dependent on head-to-SUL spacing which is altered by varying NiW or Cr layer thickness without affecting crystallography. Optimized head-to-SUL spacing is needed to gain head writeability as well as resolution.