Dependence of magnetic properties in superparamagnetic Co-granular thin films on deposition rate and effectiveness of a new pulsed DC reactive sputtering method for film fabrication with high deposition rate.

Abstract

The superparamagnetic thin films with a granular structure show a characteristic magnetization curve. In this study, Co-Al₂O₃ granular thin films were fabricated by the sputtering method with normal DC source for Co deposition, RF source for Al₂O₃ deposition, and pulsed DC reactive sputtering were used for fabrication of non-magnetic matrix of oxide or nitride of Al or Si. As a result, Co-Al₂O₃ superparamagnetic thin films with high magnetization could be obtained with high deposition rate. Very high deposition rate was obtained for fabrication of oxide or nitride films of Al or Si using the pulsed DC reactive sputtering method. This deposition rate was 5 times larger than RF sputtering method. It is expected that a sputtering method with DC source for Co deposition and pulsed DC source for matrix deposition will be effective to realize very high magnetization in the superparamagnetic granular thin films.