FREQUENCY-DEPENDENT COMPLEX PERMEABILITY IN RARE EARTH-SUBSTITUTED COBALT NONMAGNETIC TRANSITION-METAL SOFT FERROMAGNETIC AMORPHOUS THIN-FILMS

Using radio frequency (rf) sputtering, we have prepared in presence of a static magnetic field, ferromagnetic thin films of composition (Co93Zr7)100-yREy(RE=Nd,Pr,Dy,Tb... a magnetic rare earth element). This study was performed for small amounts of RE substitution (0 < y < 3). These films exhibit attractive soft magnetic properties similar to CoZr alloys: low coercivity (H(c) approximately 1 Oe), and a high saturation induction (4piM(s) > 10 Kg). A low in-plane uniaxial anisotropy H(k) was induced, whose magnitude depends upon the composition and the preparation parameters. Substitution by RE atoms affects essentially the mu frequency-response. Depending on the nature, the concentration of RE atoms and on the value of H(k), a high relative rotational permeability mu (mu' approximately 500-3000 at frequencies up to 500 MHz) was obtained. Also depending on RE and on y, high mu'' (mu'' approximately 400-3000 at nu approximately 1 GHz) distributed over a very broad frequency range (DELTAnu approximately 500-2500 MHz) could be measured.