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The effect of melting point (Tm) of various grain boundary materials (GBMs) on the magnetic properties and nanostructure of FePt granular films was investigated. According to the analysis for the granular films with a constant GBM volume of 30 vol% deposited at a high substrate temperature, the saturation magnetization, Ms, had a strong correlation with Tm. We newly proposed a degree of order evaluation from in-plane X-ray diffraction from the L10 FePt (110) and (220) planes. As the results, neither the degree of order nor the grain diameter had any significant correlation with the Tm of GBM. Based on these analyzes, it was found that an increase of the grain diameter increases the degree of order, which results in enhancement of the coercivity of the FePt granular films. And it was clarified that Ms strongly depends on the degree of phase separation related to the melting point of GBM.

Coupled granular/continuous (CGC) media are formed by depositing a 6 nm Co/Pd multilayer onto a CoCrPt-SiO 2 granular magnetic layer. The multilayer reduces magnetic saturation field from 11.4 to 7.2 kOe. The lower is reflected in the recording overwrite (OW) improvement of around 20 dB. The thermal stability factor 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 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.Index Terms-Activation volume, angular dependence of , cluster size, plane view TEM image.

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