Using structural disorder to enhance the magnetism and spin-polarization in Fe_xSi_1-x thin films for spintronics

Amorphous Fe_xSi_1-x thin films exhibit a striking enhancement in magnetization compared to crystalline films with the same composition (0.45 < x < 0.75), and x-ray magnetic circular dichroism reveals an enhancement in both spin and orbital moments in the amorphous films. Density functional theory (DFT) calculations reproduce this enhanced magnetization and also show a relatively large spinpolarization at the Fermi energy, also seen experimentally in Andreev reflection. Theory and experiment show that the amorphous materials have a decreased number of nearest neighbors and reduced number density relative to the crystalline samples of the same composition; the associated decrease in Fe-Si neighbors reduces the hybridization of Fe orbitals, leading to the enhanced moment.