Enhanced spin-orbit coupling in tetragonally strained Fe-Co-B films

• Tetragonally strained interstitial Fe-Co-B alloys were synthesized as epitaxial films grown on a 20 nm thick Au0.55Cu0.45 buffer layer. Different ratios of the perpendicular to in-plane lattice constant c/a = 1.013, 1.034 and 1.02 were stabilized 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 mainly originates from B impurities in octahedral position and the reduced symmetry around B atoms. These findings offer the possibility to enhance SOC phenomena - namely the magnetocrystalline anisotropy and the orbital moment - by stabilizing anisotropic strain by doping 4 at.% B. Results on the influence of B doping on the Fe-Co film microstructure, their coercive field and magnetic relaxation are also presented.

Ämnesord

NATURVETENSKAP  -- Fysik -- Den kondenserade materiens fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Condensed Matter Physics (hsv//eng)

Nyckelord

Fe-Co-B

ferromagnetic resonance

g-factor

magnetic anisotropy

orbit coupling

spin

tetragonal strain

x-ray magnetic circular dichroism

Binary alloys

Calculations

Copper alloys

Crystal impurities

Crystal symmetry

Dichroism

Epitaxial growth

Ferromagnetic materials

Ferromagnetism

Gold alloys

Iron alloys

Magnetic moments

Magnetic storage

Magnetocrystalline anisotropy

Semiconductor doping

Spectroscopy

X rays

G factors

Cobalt alloys

Physics with spec. in Atomic, Molecular and Condensed Matter Physics

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