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arXiv · 1911.05666

Interface-related magnetic and vibrational properties in Fe/MgO heterostructures from nuclear resonant spectroscopy and first-principles calculations

Benedikt Eggert·Markus E. Gruner·Katharina Ollefs·Ellen Schuster·Nico Rothenbach·Michael Y. Hu·Jiyong Zhao·Thomas S Toellner·Wolfgang Sturhahn·Rossitzza Pentcheva·Beatriz Roldan Cuenya·Esen E. Alp·Heiko Wende·Werner Keune
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Abstract

We combine $^{57}$Fe M\"ossbauer spectroscopy and $^{57}$Fe nuclear resonant inelastic x-ray scattering (NRIXS) in nanoscale polycrystalline [bcc-$^{57}$Fe/MgO] multilayers with various Fe layer thicknesses and layer-resolved density-functional-theory (DFT) based first-principles calculations of a (001)-oriented [Fe(8 ML)/MgO(8 ML)](001) heterostructure to unravel the interface-related atomic vibrational properties of a multilayer system. In theory and experiment, we observe consistently enhanced hyperfine magnetic fields compared to bulk which are associated with the Fe/MgO interface layers. NRIXS and DFT both reveal a strong reduction of the longitudinal acoustic (LA) phonon peak in combination with an enhancement of the low-energy vibrational density of states (VDOS) suggesting that the presence of interfaces and the associated increase in the layer-resolved magnetic moments results in drastic changes in the Fe-partial VDOS. From the experimental and calculated VDOS, vibrational thermodynamic properties have been determined as a function of Fe thickness and are found to be in excellent agreement.

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Benedikt Eggert, Markus E. Gruner, Katharina Ollefs, Ellen Schuster, Nico Rothenbach, Michael Y. Hu, Jiyong Zhao, Thomas S Toellner, Wolfgang Sturhahn, Rossitzza Pentcheva, Beatriz Roldan Cuenya, Esen E. Alp, Heiko Wende, Werner Keune. 2019-11-13. Interface-related magnetic and vibrational properties in Fe/MgO heterostructures from nuclear resonant spectroscopy and first-principles calculations. https://doi.org/10.1103/physrevmaterials.4.044402

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