X-Ray Absorption Spectra and Self-Bias Ferromagnetic Resonance of FeCoB Films Prepared by Composition Gradient Sputtering

Fe_0.7Co_0.3B films with a thickness of 100 nm were prepared by composition gradient sputtering on (100) single-crystal Si substrates. A considerable increase in uniaxial magnetic anisotropy fields H_k from 180.6 to 295.5 Oe was achieved by the gradient composition induced stress. Although the saturation magnetization 4π M_S slightly decreases from 16.3 to 13.5 kG with the increase in the B concentration, the ferromagnetic frequency f_FMR increases from 4.82 to 5.62 GHz due to the domination of H_k. The X-ray absorption spectra revealed that the decrease in the 4π M_S with B concentration can be attributed to the hybridization between Fe and B atoms.