Thermomagnetically written domains in compositionally modulated DyFeCo thin films

Magnetic properties of critical importance to the thermo-magnetic recording process are shown to be structure dependent. The use of structure as an additional tool in the control of these properties is illustrated by experiments that compare the size of domains written thermo-magnetically into different structured DyFeCo films. Samples with a common average composition and all 40 nm thick and with form that varies from the conventional homogeneous amorphous alloy to a material consisting of discrete Dy and FeCo layers, have been investigated. It is found that, whilst the Curie temperature, compensation temperature and saturation magnetization reflect the consistency of the average composition and remain constant across the range, the perpendicular anisotropy and coercivity are structure dependent and increase as the films become more layered, reaching a maximum when the rare earth (RE) layers are nominally one monolayer thick. In the writing experiments this behaviour is observed as the creation of different sized stable domains under constant write conditions.