Magnetic properties of epitaxialFe3Si∕MgO(001)thin films

Abstract

The composition dependence of the magnetic as well as structural properties of epitaxial $4--40\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ ${\mathrm{Fe}}_{3}\mathrm{Si}$ thin films on MgO(001) have been investigated using ferromagnetic resonance, superconducting quantum interference device magnetometry, and magneto-optical Kerr effect. Magnetic anisotropy energy, $g$ factor, and magnetization were determined for different samples with Si concentrations of 20%, 25%, or 30% at room temperature. Additionally, different annealing procedures were applied. The magnetization was determined to be on the order of ${\ensuremath{\mu}}_{0}M\ensuremath{\approx}1\phantom{\rule{0.3em}{0ex}}\mathrm{T}$. It was found that the films have a dominating cubic anisotropy ${K}_{4}\ensuremath{\approx}3\ifmmode\times\else\texttimes\fi{}{10}^{3}\phantom{\rule{0.3em}{0ex}}\mathrm{J}∕{\mathrm{m}}^{3}$ which depends on the thermal treatment of the film and is about 1 order of magnitude smaller than the one of bulk Fe. A small uniaxial in-plane anisotropy of interfacial nature was detected. The perpendicular uniaxial anisotropy term, which is dominated by an interface contribution, favors a perpendicular easy axis. From frequency-dependent ferromagnetic resonance measurements an isotropic $g$ factor was extracted $g=2.075(5)$ for 8 and $40\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ samples and $g=2.080(5)$ for the $4\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ one. Different thermal treatments of the sample showed no influence on the $g$ factor. The magnetic anisotropy fields and $g$ factor decrease linearly as the Si concentration increases within the $D{0}_{3}$ regime.