Magnetocrystalline anisotropy in x-ray magnetic linear dichroism at the 3$p$ edges of crystalline Fe thin films

X-ray magnetic linear dichroism spectra measured in reflection (XMLD-R) on crystalline bcc Fe thin films across the 3$p$ absorption edges are reported. A series of measurements with varying orientation of the electric field vector of the linear polarized synchrotron radiation with respect to the crystal axes reveals a strong magnetocrystalline anisotropy in the XMLD-R spectra. The spectra agree well with theoretical spectra calculated within the framework of the density-functional theory accounting for the spin-orbital and exchange splitting of the $3p$ semicore states on an equal footing.

Figure 1

Experimental geometry for the detection of XMLD-R spectra. The reflectivity $R=I_{\mathrm{out}}/I_{\mathrm{in}}$ is measured on a crystalline sample for four relative orientations of polarization $E$ and saturating field $H$ and at variable angle $\varphi$, which is defined with respect to a crystal axis, e.g., $\langle 100\rangle$. Note that in practice only one, but a rotatable, magnetic field is applied, e.g., $H_{\parallel }^{+}$.

Figure 2

XMLD-reflection spectra ($\Delta R$) measured across the 3$p$ edge of a 30 nm bcc Fe film at near-normal incidence $\theta ={85}^{\circ }$ for different orientations $\varphi$ of the $E$ field with respect to the $\langle 100\rangle$ crystal axis. The experimental results are given by the black points, the result of ab initio calculations by the full curves. The vertical lines denote the positions of the computed single $j_z$ levels of the $3p_{3/2}$ and $3p_{1/2}$ states.

Figure 3

Polar plot of the XMLD-R asymmetry $A$ measured on a 30 nm Fe film at 52.25 eV; $\varphi =0^{\circ }$ corresponds to the Fe $\langle 100\rangle$ easy axis. The full line shows an ideal sinusoidal curve with fourfold symmetry.