Atomic-Layer Resolved Magnetic and Electronic Structure Analysis of Ni Thin Film on a Cu(001) Surface by Diffraction Spectroscopy

Up until now there has been no direct method for detecting the electronic and magnetic structure of each atomic layer at the surface, which is an essential analysis technique for nanotechnology. For this purpose, we have developed a new method, diffraction spectroscopy, based on the photon energy dependence of the angular distribution of Auger electron emission. We have applied this method to analyze the magnetic structure of a Ni ultrathin film on a Cu(001) surface around the spin reorientation transition. Atomic-layer resolved x-ray absorption and magnetic circular dichroism spectra were obtained. Surface and interior core-level shifts and magnetic moments are determined for each atomic layer individually.

Figure 1

(a) Schematic diagram of analyzer. By scanning a wedged Ni film sample, the Ni LMM AED patterns of different Ni film thicknesses are projected onto the fluorescent screen sequentially. (b) Crystal orientation and screen. Pronounced FFPs appear along the directions of atoms surrounding an excited atom in the AED pattern. (c) AED patterns from various film thicknesses at the kinetic energy of 841 eV. FFPs from second-layer atoms are already present in the 1 ML AED pattern, while Kikuchi bands become apparent from the 4 ML AED pattern.

Figure 2

(a) Atomic-layer-resolved Ni $L_3$ XANES spectra from 1–3 ML Ni films obtained by measuring photon energy dependence of various FFP intensity in AED. (b) Graph and (c) color presentations of Ni $L_3$-edge peak shift from bulk for each atomic layer in various Ni film thicknesses.

Figure 3

(a) Atomic-layer-resolved Ni $L$-XANES and (b) XMCD spectra from in plane (8 ML) and perpendicularly (15 ML) magnetized Ni films. AED patterns are shown together.

Figure 4

(a) Spin magnetic moments of each atomic layer in the Ni thin film on a Cu(001) surface. (b) The ratio of orbital and spin components. The experimental [13, 27] and theoretical [15] values are shown together.