Magnetic properties of Co-Tb alloy films and Tb/Co multilayers as a function of concentration and thickness

Abstract Deposition of alloy films with a well-controlled concentration gradient obtained by co-sputtering from two magnetron sources is studied experimentally and compared with numerical calculations. This method was used together with a linearly moving shutter to fabricate sperimagnetic Co-Tb alloy films with mutually orthogonal concentration and thickness gradients. Using magnetooptical measurements it was demonstrated that, for thicknesses below 10 nm, the compensation concentration (ccomp) shifts towards higher Tb content as the thickness of the Co-Tb film is reduced. Results for Co-Tb alloy films are compared with those for (Tb/Co)RN multilayers with various repetition numbers (RN). For both sample types, the ccomp decreases in a similar way with increasing total film thickness. Thus, the decrease of ccomp with increasing total thickness (either of alloy films or of multilayers) can be considered a universal behavior.