Statistical approach for the optimal deposition of Cr underlayer for SmCo/Cr magnetic films

The quality of sputtered-deposited SmCo/Cr films used for high-density magnetic recording media depends on several sputtering factors of the Cr underlayer. Investigation into the optimal sputtering conditions needs a large number of experiments. So it is desirable to minimise the number of experiments and maximise the amount of information gained from them. The orthogonal design of experiments and mathematical statistical method are considered as effective methods to optimise the sputtering condition of the Cr underlayer for high coercivity of SmCo/Cr films. Using the orthogonal design method, the effects of the four factors, such as the target–substrate distance, the DC power, the sputtering pressure and the sputtering time, were simultaneously investigated by only nine experiments. The optimal condition of the Cr underlayer was obtained. At the optimal condition, the coercivity was promoted to 3.12 kOe. The target–substrate distance, the DC power and the sputtering pressure are very important factors for coercivity values; on the other hand, the effect of sputtering time is not obvious. It can be proved that our orthogonal design of experiment is of 95% confidence.