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
_u⊥
^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
_u⊥
^exp
was not dependent on the saturated torque coefficient of fourfold components (L
_4θ
^sat
) but was dependent on that of twofold components (L
_2θ
^sat
) originating from magnetic grains with c-axes normal to the film plane. Furthermore, L
_4θ
^sat
mainly originated from FePt grains with c-axes parallel to the film plane. K
_u⊥
^exp
also had a strong correlation with grain diameter (GD) and degree of order (Sin). On the other hand, K
_u⊥
^exp
had no significant correlation with the melting point (Tm) of the GBM, which indicates that the dominant factor affecting K
_u⊥
^exp
was not phase separation. Based on these evaluations, an increase of GD caused an increase of Sin, regardless of the GBMs, which resulted in enhancement of K
_u⊥
^exp
for the FePt granular films.