NiAl+SiO(2) thin films were used as a grain size reducing seedlayer for cobalt alloy granular perpendicular magnetic recording media. The effect of this NiAl+SiO(2) seedlayer on the microstructure and crystalline orientation of Ru intermediate layer has been investigated. By co-sputtering the composite NiAl+SiO(2) seedlayer, the smallest average grain diameter of NiAl was significantly reduced to about 2.5 nm. The grain size of the subsequent Ru intermediate layer was reduced to about 4 nm. X-ray diffraction results indicate an epitaxial orientation relationship of NiAl (110) // Ru (0002) between the two layers. Moreover, significant improvement of this epitaxial relationship was developed, which produced narrow c-axis distribution of the Ru intermediate layer with small grain size. The addition of the NiAl+SiO(2) seedlayer is a very promising approach to reduce the Ru intermediate layer grain size and eventually the magnetic layer grain size for perpendicular magnetic recording media without deterioration of other properties of thin films. Published by Elsevier B.V