Enhanced and Tunable Spin-Orbit Coupling in tetragonally Strained Fe-Co-B Films
(English)Manuscript (preprint) (Other academic)
Tetragonally strained interstitial Fe-Co-B alloys were synthesized as epitaxial films grown on Au0.55Cu0.45 buffer layer with the thickness of 20 nm. The strain axis is perpendicular to the film plane and the corresponding lattice constant c is enlarged with respect to the in-plane lattice parameter a. The tetragonal strain was stabilized in Fe-Co films with different c/a ratios of 1.013, 1.034 and 1.02 by adding interstitial boron with different concentrations 0, 4, and 10 at.%, respectively. Using ferromagnetic resonance (FMR) and x-ray magnetic circular dichroism (XMCD) we found that the total orbital magnetic moment significantly increases with increasing c/a ratio, indicating that reduced crystal symmetry and interstitial B leads to a noticeable enhancement of the effect of spin-orbit coupling (SOC) in the Fe-Co-B alloys. First-principles calculations reveal that the increase in orbital magnetic moment manly originates from B impurities in octahedral position and reduced symmetry around B atoms. These findings offers the possibility of tuning SOC phenomena - namely the magnetocrystalline anisotropy and the orbital moment - by stabilizing anisotropic strain through selection of B concentration, where B atoms preferentially occupy octahedral interstitial positions in the bct FeCo. We also discuss the influence of B doping on the Fe-Co film microstructure, their coercive field and magnetic relaxation.
magnetism, spin-orbit, magnetic anisotropy, FRM, XMCD, DFT
Condensed Matter Physics
Research subject Physics with spec. in Atomic, Molecular and Condensed Matter Physics
IdentifiersURN: urn:nbn:se:uu:diva-304518OAI: oai:DiVA.org:uu-304518DiVA: diva2:1033178