Effect of additional element (Fe, Zr, Ta) for Co-Cr films deposited by targets facing type of sputtering

Abstract

In order to improve both magnetic properties and wear resistance of Co-Cr films for perpendicular magnetic recording media, the effect of the addition of a small amount of Fe, Zr, and Ta to the Co-Cr binary alloy films has been investigated. They were deposited with a targets facing type sputtering (TFTS) apparatus. (i) The addition of a small amount of Fe (<5 at. %) causes a significant decrease of the effective perpendicular magnetic anisotropy K⊥ (K⊥=Ku−2πM2s). The K⊥ has a negative value at Fe content above 1 at. %. Consequently, the recording characteristics become worse as Fe content increases. (ii) The addition of Zr leads to a remarkable decrease of grain size and improvement of surface smoothness along with an increase of wear resistance. It also causes evident decrease in Ku and saturation magnetization Ms. However, both K⊥ and remanence ratio Mr⊥/Mr∥ are increased by the addition of a small amount of Zr up to 0.5 at. %, though they decrease steeply with further increase of Zr content above 1 at. %. (iii) The addition of Ta shows almost the same tendency as Zr for the film structure and wear resistance. It also causes the decrease of Ku. But the K⊥ increases with an increase of Ta content up to 0.5 at. % and takes nearly constant value at Ta content above 0.5 at. %, since the Ms of the film decreases remarkably as Ta content increases. Mr⊥/Mr∥ increases gradually from 2.5 to 3.6 as Ta content increases. Consequently, the addition of a small amount of Ta is effective for improving both recording characteristics and wear resistance.