THERMOMAGNETICALLY WRITTEN DOMAINS IN COMPOSITIONALLY MODULATED DYFECO THIN-FILMS

Magnetic properties of critical importance to the thermo-magnetic reco rding process are shown to be structure dependent. The use of structur e as an additional tool in the control of these properties is illustra ted by experiments that compare the size of domains written thermo-mag netically into different structured DyFeCo films. Samples with a commo n average composition and all 40nm thick and with form that varies fro m the conventional homogeneous amorphous alloy to a material consistin g of discrete Dy and FeCo layers, have been investigated. It is found that, whilst the Curie temperature, compensation temperature and satur ation magnetization reflect the consistency of the average composition and remain constant across the range, the perpendicular anisotropy an d coercivity are structure dependent and increase as the films become more layered, reaching a maximum when the rare earth (RE) layers are n ominally one monolayer thick. In the writing experiments this behaviou r is observed as the creation of different sized stable domains under constant write conditions.