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 L1 0 -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.