Spin and orbital magnetic moment of reconstructed $\sqrt{2}\times \sqrt{2}R{45}^{\circ }$ magnetite(001)

The surface of a magnetite single crystal with (001) orientation has been prepared by sputtering/annealing cycles providing the $\sqrt{2}\times \sqrt{2}R{45}^{\circ }$ reconstruction. The distribution of magnetic domains on the surface has been imaged by x-ray magnetic dichroism in a photoemission microscope. The easy axes are along the surface in-plane $\langle 110\rangle$ directions. The near-surface magnetic moment was determined by applying the sum rules to XMCD spectra obtained with different kinetic energies of the secondary electrons. A reduced total moment of $3.3 {\mu }_B$ and a ratio of about 0.10 between orbital and spin moment was found, which we attribute to the surface reconstruction.

Figure 1

(a) Low-energy electron microscopy image of the surface of the magnetite crystal, acquired at an electron energy of 5.5 eV. (b) LEED pattern showing the $\sqrt{2}\times \sqrt{2}R{45}^{\circ }$ reconstruction, acquired at 32 eV. (c) Dark-field image using one of the first order beams. (d) XMCD-PEEM image showing magnetic domains. (e) XMLD-PEEM with in-plane polarization. (f) XMLD-PEEM with vertical polarization. All the LEEM and PEEM images are acquired in the same area, and the same feature is highlighted with a yellow square in each one as a guide to the eye. The LEEM and PEEM images are $14 \mu \mathrm{m}$ wide. (g) XPS spectra from the surface, acquired from a sequence of PEEM images.

Figure 2

(a) Averaged XAS spectra, from individual spectra measured with positive and negative helicity. XMCD spectra acquired from sequences of images detecting electrons with two different kinetic energies, (b) with low kinetic energy ($\sim 2$ eV), and (c) 50 eV. In both cases the XMCD spectra have been calculated by varying the photon energy and measuring the intensity of the PEEM images in two adjacent domains with opposite magnetization, and averaging the result with the two helicities.