Molecular beam epitaxy and crystal structure of majority a-plane-oriented and substrate-strained Mn3Sn thin films grown directly on sapphire (0001).

The Kagome antiferromagnet Mn 3 Sn has garnered much attention due to the presence of exciting properties such as anomalous Hall and Nernst effects. This paper discusses the synthesis of crystalline Mn 3 Sn thin films, prepared on Al 2 O 3 (0001) substrates at 453 ± 5 ° C using molecular beam epitaxy. The growth is monitored in situ using reflection high energy electron diffraction and measured ex situ using x-ray diffraction, Rutherford back-scattering, and cross-sectional scanning transmission electron microscopy. Our analysis shows the in-plane lattice constants of a 1 , M = 4.117 ± 0.027 Å and a 2 , M = 4.943 ± 0.033 Å, which is a very unexpected result when compared to the bulk a -plane Mn 3 Sn. This indicates a strain in the film and makes it challenging to provide a straightforward explanation. In an effort to explain our results, we discuss two possible orientation relationships between the Mn 3 Sn films and the sapphire substrates. Samples prepared under these conditions appear to have smooth surfaces locally, but overall the film has a 3D island morphology. First-principles calculations provide atomic models of the Mn 3 Sn (11 2 ¯ 0) lattice on Al 2 O 3 (0001) high symmetry sites, indicating that the L3-R90 ° is the most stable configuration. A detailed discussion of the experimental data and theoretical results, as well as strain effects, is provided. [ABSTRACT FROM AUTHOR]