Amorphous Tb20Fe80/Al2O3 multilayers (abstract)

We have prepared amorphous Tb20Fe80/Al2O3 multilayer films by rf sputtering onto water-cooled glass substrates using 100-W rf power and argon pressure of 6 mT. The thickness of the Al2O3 layer was kept constant at 4 nm and that of Tb-Fe (denoted as d) was varied from 4 to 10 nm. The total number of bilayers was in the range 10–15. A single layer of Tb-Fe of 200 nm was also prepared to serve as a reference. All the films were given a protective Al2O3 layer of about 15 nm thick. Magnetization (M) and a hysteresis loop were obtained using a VSM. Uniaxial anisotropy (Ku) and M were measured with a torque meter. Polar Kerr loops were taken with a HeNe laser. For d>6 nm M remains the same but increases sharply for d8 nm. This would indicate that the microscopic mechanisms for these two properties are not the same. Finally, only samples with d>8 nm show all the characteristics of the thick single layer. Detailed analysis of the torque curves will be presented.