High $K_{{{u}}}$ and Low Intergranular Exchange Coupling of Postannealed CoPt-WO3 Granular Film

Magnetic properties and microstructure of Co
₈₀
Pt
₂₀
-30 vol.% (Al
₂
O
₃
, TiO
₂
, WO
₃
) and Co
_82.4
Pt
_17.6
-27.7 vol.% SiO
₂
granular films postannealed at various temperatures in a heat-treating furnace were investigated. In this paper, it is found that among these granular films, CoPt-WO
₃
granular film shows the highest coercivity (
${H_{c}}$
) because of low intergranular exchange coupling of well-isolated magnetic grains. Furthermore, the
${H_{c}}$
is enhanced with postannealing because of the increase of the magnetic anisotropy field (
${H_{k}^{\mathrm {grain}}}$
) and uniaxial magnetocrystalline anisotropy (
${K_{u}^{\mathrm {grain}}}$
) of the columnar growth magnetic grains. The increase of
${K_{u}^{\mathrm {grain}}}$
for the postannealed granular film primarily originates from the reduction of the stacking faults as well as the lattice constant ratio.