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Magnetic properties and nanostructure for FePt-30vol%TiN deposited while flowing N2gas are investigated. When N2gas addition of 3%–5% are introduced, compared with that of without N2gas, reduction in the lattice constant ratio and the unit cell volume, the increase in the degree of order of the granular film are observed. These indicate the segregation of Ti into grain boundaries as the result of the N2gas addition through nitridization of Ti dissolved in the FePt grains which lead to the enhancement of saturation magnetization, perpendicular magnetic anisotropy, and magnetic anisotropy field of the granular film. Therefore, magnetic decoupling in the FePt-TiN similar to the FePt-BN granular films is promoted by the segregation of nitrides formed by nitridization of metal element solidly soluble in FePt magnetic grains due to nitrogen deficiency.

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 L10FePt (110) and (220) planes. As the results, neither the degree of order nor the grain diameter had any significant correlation with the Tmof 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 Msstrongly depends on the degree of phase separation related to the melting point of GBM.

The magnetic properties and microstructure of Co80Pt20-30 vol % B2O3 granular medium deposited on nucleation layers (NLs) with Co80Pt20-30 vol % oxides (oxides: Nb2O5, WO3, Ta2O5, SiO2, TiO2, Al2O3, Cr2O3, and ZrO2) of various thicknesses were investigated. By introducing an NL, a granular medium with columnar growth of small magnetic grains can be obtained. Furthermore, magnetic grains are separated with an oxide grain boundary material from the initial growth region that promotes the decoupling of magnetic grains, which corresponds to an increase in coercivity. The degrees of diameter reduction and decoupling of magnetic grains depend on the NL thickness and the melting point of the oxide utilized in the NL.

The magnetic properties and structures of Co80Pt20-30 vol % oxide (ZrO2, Cr2O3, Y2O3, Al2O3, MnO, TiO2, WO2, SiO2, Mn3O4, WO3, Co3O4, MoO3, and B2O3) granular media deposited at room temperature were investigated. As a result, the following were found. 1) By employing oxides with low melting point temperatures as the granular media, magnetic grains with high saturation magnetization ($M_{\text{s}}^{\text{grain}}$) and perpendicular magnetic anisotropy ($K_{\text{u}}^{\text{grain}}$) are obtained; the increases in $M_{\text{s}}^{\text{grain}}$ and $K_{\text{u}}^{\text{grain}}$ are due to the promotion of the columnar growth of magnetic grains and phase separation or two-phase precipitation between magnetic grains and oxides. 2) The increase in the $K_{\text{u}}^{\text{grain}}$ of the granular media followed by the decrease in the melting point of oxides is due to the reduction in the amount of stacking faults. 3) Among these granular media, the CoPt-B2O3 granular medium has the highest coercivity (H c) and ratio of H c to the magnetic anisotropy field ($H_{\text{c}}/H_{\text{k}}^{\text{grain}}$) of 8.0 kOe and 0.4, with $M_{\text{s}}^{\text{grain}}$ and $K_{\text{u}}^{\text{grain}}$ of 1115 emu/cm3 and 1.1 x 107 erg/cm3, respectively. 4) The CoPt-B2O3 granular medium has well-isolated and columnar growth magnetic grains with an average grain size of 6.5 nm.