To improve magnetic properties, an magnetic reversal process and read/write(R/W) characteristics on an SmCo_5 perpendicular magnetic thin films, we introduced pinning sites into the SmCo_5 thin film. In this study, we added carbon(C) atoms into a Cu underlayer as pinning sites. C atoms were diffused up to the Sm-Co magnetic layer during Sm-Co deposition. As a result, the magnetic exchange interactions among the Sm-Co grains were decreased. And then the magnetic domain cluster size became small and magnetization reversal process was changed from a wall-motion magnetization reversal mode to a coherent rotation magnetization reversal mode by adding C atoms into Cu underlayer. We also evaluated the R/W characteristics of SmCo_5 perpendicular double-layerd media. The medium noise was decreased and signal-to noise ratio was increased by introducing the C. The addition of C into the Cu underlayer is effective reducing medium noise and increasing SNR.
