DEPENDENCE OF THE POLAR KERR ANGLE AND COERCIVITY ON REPEAT DISTANCE IN SEQUENTIALLY PREPARED TB/FECO FILMS

Abstract

Multilayer thin films of Tb and FeCo were prepared by sequential thermal evaporation of Tb and Fe90Co10 alloy on glass substrates at ambient temperature in a vacuum of about 1 X 10(-6) Torr. The repeat distance of the films was varied from 3.5 to 175 angstrom while maintaining the composition constant for all samples. Low-angle x-ray diffraction and Auger electron spectroscopy showed that a multilayer structure was achieved for films fabricated with a repeat distance LAMBDA greater-than-or-equal-to 31.5 angstrom. The polar Kerr rotation angle and coercivity of the samples were obtained by measuring the polar Kerr hysteresis loop using a 632.8-nm HeNe laser. It was observed that for the samples having a multilayer structure, the remnant Kerr angle and coercivity monotonically decreased with increasing repeat distance, and eventually disappeared for LAMBDA greater-than-or-equal-to 70 angstrom. For the samples showing a nonmultilayer structure, the remnant Kerr angle was independent of repeat distance. However, the coercivity increased with repeat distance until a broad maximum was obtained around LAMBDA congruent-to 14-21 angstrom.