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

Abstract

Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.7</sub> Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.3</sub> B 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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</sub> from 180.6 to 295.5 Oe was achieved by the gradient composition induced stress. Although the saturation magnetization 4π M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</sub> slightly decreases from 16.3 to 13.5 kG with the increase in the B concentration, the ferromagnetic frequency f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">FMR</sub> increases from 4.82 to 5.62 GHz due to the domination of H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</sub> . The X-ray absorption spectra revealed that the decrease in the 4π M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</sub> with B concentration can be attributed to the hybridization between Fe and B atoms.