Aspects of the present invention relate to a perpendicular magnetic recording (PMR) media stack and methods for fabricating the same. The PMR media stack has a novel grain isolation initiation layer (GIIL) and/or a novel exchange-break layer (EBL) that can improve the signal-to-noise performance of the PMR media stack. The PMR media stack includes a substrate, a soft underlayer on the substrate, an interlayer positioned on the soft underlayer, and a grain isolation initiation layer (GIIL) positioned on the interlayer, a magnetic layer positioned on the GIIL, and an exchange break layer (EBL) positioned on the magnetic layer. The GIIL and/or EBL includes a CoCrRu-oxide.