| Popis: |
In this thesis, ultra-thin films of MnxAu1−x have been studied structurally and magnetically. We prepared the thin films with electron-beam evaporators in ultrahigh vacuum (UHV). The growth of the films was monitored by medium-energy electron diffraction (MEED). The films’ structures were investigated by means of low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM), and the chemical composition was checked by Auger electron spectroscopy (AES). The magnetic property of the antiferromagnetic (AFM) films in contact with FM films was studied by longitudinal magneto-optic Kerr effect (L-MOKE), X-ray magnetic circular dichroism (XMCD), and X-ray resonant magnetic reflectivity (XRMR) spectroscopy at L2,3 absorption edge. AFM Mn2Au might be very significant for future spin-electronic applications. We studied MnxAu1−x films in detail to investigate their structure for a variety of thicknesses on Cu(001) and Ag(001) single crystals. First, we studied Au/Mn/Co on Cu(001) to define the growth rate for Au, Mn, and Co using MEED. The vertical interlayer distances for Co on Cu(001) and Mn on Co/Cu(001) and surface topography of Au on Mn/Co/Cu(001) were investigated by LEED-I(V) (00 spot intensity was recorded vs. electron beam energy) and STM, respectively. After that, we studied from sub-ML (surface coverage of less than one monolayer) to more than 1ML of MnxAu1−x on Cu(001) structurally by LEED and STM. We observed a c(2×2) superstructure for coverages between 0.5 and 1ML of MnxAu1−x on Cu(001). MnxAu1−x revealed MEED oscillations during growth on Cu(001), but no LEED patterns could be observed for thicker films (> 1 ML). For studying the magnetic properties of AFM MnxAu1−x on Cu(001), we grew Co on top, then we employed MOKE after zero-field cooling as well as after field cooling. We observed coercivity changes with temperature, however, we did not observe any exchange bias. Finally, we studied Mn and MnxAu1−x growth on Ag(001) to define the growth rate and structure of the resulting films. Fe growth on Ag(001) was also studied structurally. We deduced vertical interlayer distances for single-layer and bilayer films (Fe, MnxAu1−x) on Ag(001) from a kinematic analysis of LEED-I(V) curves because both show LEED patterns. The MnxAu1−x showed MEED oscillations during growth on Ag(001). Fe/MnxAu1−x bilayers on Ag(001) were studied magnetically by MOKE.We did not observe any significant change in coercivity to confirm the antiferromagnetism of the MnxAu1−x films. |
