High-Frequency Magnetic Loss in Nanogranular FeCoTiO Films With Different Histories of Induced Uniaxial Anisotropy

Nanogranular FeCoTiO magnetic films have been deposited on Si substrates by magnetron sputtering. An in-plane uniaxial anisotropy field was induced by either applying in situ biasing magnetic field (H
_bias
) during growth or tilting the substrate to a certain oblique angle. It was found that a stable anisotropic field close to 80 Oe could be induced by an H
_bias
field as small as 15 Oe. Permeability spectrum measurements show that both the ferromagnetic resonance frequency and the effective damping factor (α
_eff
) are insensitive to the magnitude of H
_bias
for H
_bias
≤ 900 Oe. Although the oblique sputtered FeCoTiO films show a larger coercive field than those deposited under H
_bias
, smaller α
_eff
can be obtained upon selecting a proper oblique angle. Therefore, the overall high-frequency magnetic loss of oblique sputtered FeCoTiO films is still much smaller than those deposited under in situ H
_bias
in a frequency range between 200 MHz and 2 GHz.