Effect of CrW underlayer on structural and magnetic properties of FePt thin films

$L10$ ordered FePt thin films with face-centered-tetragonal (001) texture have been prepared by magnetron sputtering on $Cr100−xWx$ underlayer. The dependence of $Cr100−xWx$ microstructure and FePt texture on the W content in the Cr underlayer was investigated. The addition of W element in Cr underlayer enhances the Cr (200) texture and increases the lattice constant of Cr, which is favorable for lowering the transformation temperature from fcc to fct phase because of the increase of the tensile stress along the FePt $a$ axis. A good FePt (001) texture is obtained on the $Cr85W15$ underlayer with a substrate temperature of $400°C$⁠. The coercivity of FePt thin films on CrW underlayer is higher than on Cr underlayer and increases with increasing W content in the Cr underlayer because the formation of the CrW alloy inhibits the diffusion between FePt and CrW layer. A $5nm$ Pt intermediate layer was employed to suppress the diffusion between FePt and CrW underlayer further.