Influence of Ferromagnetic Layer Composition on Perpendicular Exchange Anisotropy in Pt/Co$_{1-x}$Ni$_{x}$/ $\alpha$-Cr $_{2}$O $_{3}$ Thin Films

We investigated the perpendicular exchange anisotropy of Pt(111)/Co
_1-
x
Ni
x
(111)/α-Cr
₂
O
₃
(0001) thin films. In order to address the inherent influence of the ferromagnetic layer composition, we also investigated the structure and the change in the perpendicular magnetic anisotropy (PMA) with the ferromagnetic layer composition. From the ferromagnetic layer thickness dependence of the PMA energy density, the interface contribution to the PMA was determined. The results suggest that the PMA is induced at the Co
_1-
x
Ni
x
(111)/α-Cr
₂
O
₃
(0001) interface as well as at the Pt(111)/Co
_1-
x
Ni
x
(111) interface. Below the Ni composition of 0.5, the high perpendicular exchange anisotropy of about 0.34 erg/cm
²
was observed. The perpendicular exchange anisotropy energy is insensitive to the ferromagnetic layer composition, which should be explained by the interfacial uncompensated antiferromagnetic spins.