Sputtered Co-Cr films: effect of substrate bias voltage on Cr concentration

Co-Cr films were prepared by RF diode sputtering on sputter-etched substrates. Varying the bias voltage V_b from 0-300 V, the saturation magnetization M_s decreases drastically with increasingV_b. In the range of low V_b values this effect can be explained by homogenization of the Cr distribution. For V_b larger than -100 V, the further reduction of M_s is a consequence of the increasing Cr concentration in the Co-Cr film from 21 at.% (V_b=-100 V) up to 27 at.% (V_b-300 V).