Perpendicular Magnetic Anisotropy Analysis for L10-Typed FePt Granular Media With Various Grain Boundary Materials by 90 kOe Torquemetry.

Perpendicular 90 kOe torquemetry analysis of magnetic anisotropy ($K_{\mathrm {u\bot }}^{\mathrm {exp}}$) for L10-typed FePt granular media with various grain boundary materials (GBMs) was conducted. According to the analysis for granular films with a constant GBM volume of 30 vol% deposited at a high substrate temperature, $K_{\mathrm {u\bot }}^{\mathrm {exp}}$ was not dependent on the saturated torque coefficient of fourfold components ($L_{4\theta }^{\mathrm {sat}}$) but was dependent on that of twofold components ($L_{2\theta }^{\mathrm {sat}}$) originating from magnetic grains with $c$ -axes normal to the film plane. Furthermore, $L_{4\theta }^{\mathrm {sat}}$ mainly originated from FePt grains with $c$ -axes parallel to the film plane. $K_{\mathrm {u\bot }}^{\mathrm {exp}}$ also had a strong correlation with grain diameter ($GD$) and degree of order ($S_{\mathrm {in}}$). On the other hand, $K_{\mathrm {u\bot }}^{\mathrm {exp}}$ had no significant correlation with the melting point ($T_{m}$) of the GBM, which indicates that the dominant factor affecting $K_{\mathrm {u\bot }}^{\mathrm {exp}}$ was not phase separation. Based on these evaluations, an increase of $GD$ caused an increase of $S_{\mathrm {in}}$ , regardless of the GBMs, which resulted in enhancement of $K_{\mathrm {u\bot }}^{\mathrm {exp}}$ for the FePt granular films. [ABSTRACT FROM AUTHOR]