The influence of the segregated microstructure on the magnetization reversal in CoCr films

The angular dependences of the Hc, Hcr, orientation ratio (OR), hysteresis loss (Wh) as a parameter of the applied field and the dependence of the distribution of hysteresis loss (DWh) on the applied field have been systematically investigated with respect to the degree of Cr segregation in CoCr films. Starting with synthetical investigation of the microscopic phenomena and macroscopic measurement results, we attempt to explain the correlation of the segregated microstructure to the magnetization reversal mechanism in CoCr films. As the substrate temperature (Ts) increases from RT to 300oC, leading to an increase in the degree of the separation in CoCr films, all the Ms, Hc, OR, anisotropy constant and nucleation field (Hn) obviously increase. On the contrary, as Ts increases the stripe-domain configuration will gradually disappear. There is a continuous transition between the domain-wall motion and rotational reversal, depending on the Ts and the heat-treatment. Combining the TEM observation of segregated microstructure with the measured results of magnetic behaviour, the magnetization reversal for a partly segregated film is considered as the superposition of the domain-wall with perpendicular and in-plane orientation of the magnetization. However, in the case of a fully segregated film, it is thought to be the superposition of a cos type of perpendicular incoherent rotation reversal with in-plane domain-wall motion. Based on the above assumption, it was found that the measured angular dependences of the coercivity are in good agreement with the calculated ones for partly and fully segregated CoCr films. Experimental data show that the annealing treatment is favourable for improving the perpendicular recording properties in CoCr films.