Magnetic Properties and Flux Reversal in Co-Cr Films Sputtered on Low Temperature Substrates

Co-Cr films were prepared on polyimide substrates at temperatures Ts = 27°C and Ts ≫ 150°C by rf sputtering, while applying a magnetic field Ha of up to 41 Oe normal to the substrate, and/or a negative substrate bias voltage VB of up to 150 V. The films prepared at Ts = 27°C have good c-axis orientation (¿¿50 = 3.2°) and show magnetization values near those of the bulk material. In these films, we were able to obtain reentrant perpendicular hysteresis loops having a low coercivity Hc (¿) and a sharp shoulder, and could observe stripe domains with a width of about 0.3 ¿m as well as clear wall motion by the Bitter method. The application of Ha induces a change in the Cr content, saturation magnetization Ms and perpendicular anisotropy Ku. The c-axis orientation is improved by applying a VB of up to 50 V, after which the value of ¿¿50 rises. In films deposited at Ts = 150°C, the values of Ms, Ku and Hc (¿) are higher, and the c-axis orientation worse, than in films formed at Ts = 27°C.