Structural, electronic, and magnetic properties of europium films epitaxially grown on W(110)

Abstract

This study presents a detailed spin-polarized scanning tunneling microscopy (SP-STM) analysis on the structural, electronic, and magnetic properties on europium (Eu) films epitaxially grown on a W(110) substrate. Utilizing optimized growth parameters, we conduct a thickness-dependent series ranging from the submonolayer regime to films as thick as 650 AL. Atomically resolved STM images of a 130 AL Eu film unveil lateral periodic sequences of bcc(110)-ordered dislocation lines sandwiched between adjacent hcp(0001) segments, effectively relieving stress within the films. These dislocation lines exhibit a periodicity of ptopo = (3.36 +/- 0.11) nm. Tunneling spectroscopy reveals that the surface of Eu films hosts a pronounced double-peak structure at about Ubias approximate to +0.30 V and +0.48 V, corresponding to unoccupied sample states. It is interpreted as an exchange-split dz2-like surface state which remains robust even within the bcc(110) structure of the dislocation lines. Magnetically sensitive data reveal a spin spiral with a surface periodicity of pmag = (2.76 +/- 0.19) nm. The results are discussed in terms of bulk-terminated spin spirals in hcp Eu which propagate along (1123) directions in the surface-near region.