Segregation structure of bias-sputtered CoCr/Cr and CoCrTa/Cr films

The dependence of the fine Cr segregation structure in CoCr/Cr and CoCrTa/Cr films on negative bias voltage (V_B) is examined with a high resolution scanning electron microscope. The relationship between the structure and the magnetic properties is discussed. The Cr segregation in the grains is enhanced by a bias voltage of up to -90 V, resulting in an increase in H_C and M_S. Further increasing V_B results in the homogeneous distribution of Cr in the grains and an enhancement of the Cr segregation to grain boundaries from the inside of grains and the Cr underlayer. Such microstructural change causes a decrease in M_S and an increase in H_C. In the case of CoCrTa films, the effect of V _B is more pronounced than the case of CoCr films, where the Ta atoms also precipitate at grain boundaries