Abstract
The ultraclean sputtering process was newlyintroduced in the fabrication of CoNiCr and CoCrTa thin film media to establish a new concept in controlling microstructure. UC-process enables the realization of high H_c in both CoNiCr and CoCrTa media. This high H_c is mainly due to the realization of large magnetocrystalline anisotropy field of grains and low intergranular exchange coupling. UC-process realizes the adequate separation of grains by segregated grain boundaries even in media with thin Cr thickness of 2.5 nm, and enables grain size reduction without the remarkable increment in intergranular exchange coupling. In these media, the reduction of the grain size is most effective for the improvement of S/N_m.