Short-range order effects in amorphous Fe_xSi_1-x/Si multilayers induced by preparation conditions

Abstract
Magnetic properties of compositionally modulated Fe_xSi_1-x/Si amorphous multilayers are reported. The concentration x was 0.68 ≤ x ≤ 0.82 for two nominal modulation lengths λ of 4 and 8 Å. The samples were prepared by pulsating two-cathode sputtering. From SQUID magnetometry and transverse magneto-optic Kerr effect, we detected a noticeable decrease in both magnetization and relative reflectivity (δ=ΔR/R) as λ increases from 4 to 8 Å. Also, for a fixed value of x, it was found that both coercive field and in-plane uniaxial anisotropy constant decrease systematically for increasing λ. The two pulses used in the preparation method causes slight chemical short range effects, altering also the magnetic properties by changing the number and nature of nearest neighbors of a given Fe atom. The above short-range effects are present even when no multilayer structure is detected by x-ray diffraction.