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

Authors :
Eggert, Benedikt
Gruner, Markus E.
Ollefs, Katharina
Schuster, Ellen
Rothenbach, Nico
Hu, Michael Y.
Zhao, Jiyong
Toellner, Thomas S
Sturhahn, Wolfgang
Pentcheva, Rossitzza
Cuenya, Beatriz Roldan
Alp, Esen E.
Wende, Heiko
Keune, Werner
Source :
Phys. Rev. Materials 4, 044402 (2020)
Publication Year :
2019

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.<br />Comment: 14 pages, 6 figures

Details

Database :
arXiv
Journal :
Phys. Rev. Materials 4, 044402 (2020)
Publication Type :
Report
Accession number :
edsarx.1911.05666
Document Type :
Working Paper
Full Text :
https://doi.org/10.1103/PhysRevMaterials.4.044402