The role of oxygen in oblique-deposited CoNi thin films

Some effects due to the introduction of oxygen during oblique deposition of CoNi films on both the magnetic properties and the columnar structure of the deposited film are described. A double-peak variation of the in-plane coercivity with the oxygen flow rate is proposed to be due to competing contributions from (i) a shape transition in the columnar structure, and (ii) the segregation of oxygen and formation of oxides in and around the polycrystalline columns influencing both the nucleation and pinning of reverse domains and domain walls. Typically, films deposited at a low-oxygen flow rate have a curved-columnar structure, whereas above a critical, high-oxygen flow rate, the films have a straight canted-columnar morphology.