Magnetic and Read–Write Properties of Coupled Granular/Continuous Perpendicular Recording Media and Magnetization Reversal Process

Abstract

Coupled granular/continuous (CGC) media are formed by depositing a 6 nm Co/Pd multilayer onto a CoCrPt-SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> granular magnetic layer. The multilayer reduces magnetic saturation field H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> from 11.4 to 7.2 kOe. The lower H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> is reflected in the recording overwrite (OW) improvement of around 20 dB. The thermal stability factor K <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">u</sub> V/k <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</sub> T also increases with addition of the multilayer, from 60 to 100, resulting in the improvement of thermal stability for CGC media. The origin of the K <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">u</sub> V/k <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</sub> T increase derives from the larger activation volume. The CGC media has coherent magnetization reversal and very weak exchange coupling, similar to the base granular media. The coherent magnetization reversal with very weak exchange coupling contributes to a signal-to-noise-ratio (SNR) improvement of around 1 dB. These results suggest that CGC media have a recording advantage over the conventional structure media, and are a promising approach to avoid the limitations of the "magnetic recording tri-lemma" and realize future ultrahigh density recording media