Ta additive effect on RF magnetron sputtered CoCr films

Magnetic properties for sputtered CoCrTa films (18 at.% Cr and 2.0-3.0 at.% Ta), which were deposited under various background pressures P_i, and argon sputtering pressures, P _Ar, have been examined. The perpendicular anisotropy field H_k for CoCrTa films maintains high values of 5-6 kOe in a wide range of P_i and P_Ar , as compared with that for CoCr films. In order to optimize Ta composition, magnetic properties and crystalline microstructures for Ta additive content (0-4.0 at.%) have been investigated. H_k and perpendicular coercivity H_c⊥ increase with increasing Ta concentration above 2.0 at.% Ta. C-axis orientation is improved by adding Ta to CoCr films. However, above 3.0 at.% Ta, H_c⊥ steeply decreases and domain wall motion is observed, owing to the increase in crystalline grain size. The appropriate Ta composition is 2.0-3.0 at.%