This title appears in the Scientific Report :
2013
Please use the identifier:
http://hdl.handle.net/2128/5384 in citations.
High-energy high-momentum surface spin waves of ultrathin epitaxial 3d transition metal films
High-energy high-momentum surface spin waves of ultrathin epitaxial 3d transition metal films
Surface spin waves on 3d ferromagnetic films are studied in the large wave vector regime with the help of a recently developed high resolution electron energy loss spectrometer. As a first study, face centered cubic (fcc) cobalt films were prepared by the epitaxial growth of cobalt on Cu(100). Spin...
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Personal Name(s): | Jayaraman, Rajeswari (Corresponding author) |
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Contributing Institute: |
Elektronische Eigenschaften; PGI-6 |
Imprint: |
Jülich
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
2013
|
Physical Description: |
IX, 135 S. |
Dissertation Note: |
Universität Duisburg-Essen, Diss., 2013 |
ISBN: |
978-3-89336-890-7 |
Document Type: |
Dissertation / PhD Thesis |
Research Program: |
Spin-based and quantum information |
Series Title: |
Schriften des Forschungszentrums Jülich. Reihe Schlüsseltechnologien / key technologies
68 |
Subject (ZB): | |
Link: |
OpenAccess |
Publikationsportal JuSER |
Surface spin waves on 3d ferromagnetic films are studied in the large wave vector regime with the help of a recently developed high resolution electron energy loss spectrometer. As a first study, face centered cubic (fcc) cobalt films were prepared by the epitaxial growth of cobalt on Cu(100). Spin waves were probed along the [110]- and the [010]-direction with in-plane wave vectors ranging from 0.02nm$^{-1}$ to 0.1nm$^{-1}$. The directional anisotropy in the surface spin wave dispersion is found to be very small in this system. In the low wave vector regime (wave vector < 0.035nm$^{-1}$), standing spin wave modes are observed in addition to the surface spin waves. In cobalt, like in other transition metal ferromagnets, the 3d electrons are not localized. Rather they form a band of considerable width which offers the possibilityfor spin-flip excitations (Stoner-excitations) in a wide energy-momentum range. The damping of spin waves by Stoner excitations results in large energy width of the spin wave signals. For the well-defined spin waves of cobalt, the line-widths of the surface spin wave signals were quantitatively determined. As a next step, epitaxial nickel films were prepared by deposition on Cu(100). In agreement with earlier unpublished work, no spin wave excitation is observed in Ni by inelastic electron scattering presumably due to the strong damping of the spin waves. As an attempt to study the effect of nickel on cobalt surface spin waves, layers of Ni were deposited on top of Co/Cu(100). Spin waves are seen for up to three monolayers of Ni. By a careful study of the intensity of spin waves as a function of Ni layer thickness, it is proven that spin waves are localized at the Co side of the Ni/Co interface. The presence of Ni broadens the spin wave peak compared to bare Co spin waves, indicating additional decay channels provided by the nickel capping layer. The 3d-band of copper is fully occupied, and hence copper has less low energy excitations. As a consequence, the mean free path of electrons in copper is much larger than in nickel. This provided the opportunity to look at spin waves localized at the Co interface through thicker layers (up to $\approx$ 12 layers) of copper. A similar spin wave broadening as for nickel is observed for copper. One of the extensively studied systems in thin film magnetism is Fe/Cu(100) due to its richness in structural and magnetic phenomena. At least three different magnetic phases can be stabilized depending on the film thickness. In this thesis, surface spin waves of three to five monolayer iron films were studied. From the similarity to the surface spin wave dispersion of bcc Fe films, it is concluded that the observedspin waves arise from the so-called $\textit{nanomartensitic}$ phase. The nanomartensitic phase is locally similar to a bcc structure, however lacking the perfect long range order of the latter. The spin wave dispersion measured on iron films deposited on fcc Co(100) is found to be nearly identical to that of Fe/Cu(100), indicating the structural similarity of the two systems. |