Out-of-plane and in-planeM-H loops of the rapid-annealed FePt
films at various temperatures are presented in Fig. 2. For the sample
annealed at 500 C (Fig. 2 (a)), a longitudinal magnetic anisotropy
with out-of-plane coercivity (Hc) of 2.5 kOe was found owing to a
LOF value of 0.138. Although the LOF dramatically enhances
from 0.138 to 0.88 with increasing Ta from 450 to 650 C
(Fig. 2(b)e(c)), the magnetic anisotropy barely evolves from longitudinal
to isotropic state. A significant evolution of magnetic
anisotropy from isotropic to perpendicular behavior was observed
as annealing temperature was raised up to 700 C (Fig. 2(d)). The
FePt film annealed at 700 C shows excellent PMA with out-ofplane
Hc of 9.1 kOe and in-plane Hc of 1.6 kOe. The in-plane MH
loop exhibits a slight hysteresis at low applied field owing to the caxis
distribution in the perpendicular direction. For the highest Ta of
800 C, an excellent PMA with out-of-plane Hc of 10.0 kOe and inplane
Hc of 0.1 kOe was achieved. The (001) textured L10-FePt film
with Ts ¼ 800 C exhibited a high perpendicular magneticanisotropy of 2.7 ± 1.3 107 erg/cm3, based on the results published
elsewhere [20]. One may notice that the significant change in
LOF and S occurs at 500e550 C, which seems to be inconsistent
with the change in magnetic anisotropy (around 700 C). To fully
analyze the variation in texture quantitatively, the pole figure is
required to obtain the orientation distribution of crystalline lattice
from all directions of a material. However, this is a time-consuming
and difficult technique for thin film materials with thicknesses less
than 10 nm. The semi-quantitative LOF provide the texture distribution
only along the normal direction of the FePt films. One the
other hand, the magnetic anisotropy of FePt strongly depends on
the easy axis distribution. In some cases, the FePt thin films with
high LOF values barely exhibited a magnetically isotropic state due
to the wide distribution of easy axis [12,21,22]. Because the magnetic
anisotropy is much sensitive to the c-axis distribution than
the LOF, the discrepancy between magnetic properties and LOF on
Ts occurs.