Atomic scale analysis of Kagome Mn 3 Ge surfaces: effect of defects on their stability and magnetic arrangement*

Mn3Ge crystallizes in a hexagonal phase that belongs to the spatial group P63/mmc. It is a non-collinear antiferromagnetic material with a triangle-like magnetic arrangement. It is also a topological material that has attracted the attention of the scientific community. In order to reach applications in real devices, surface effects must be carefully analyzed at an atomic scale. Upon surface relaxation, the first surface layer gets shifted in the c-direction, contracting the interlayer distance with the second monolayer, which increases the magnetic moment by 20% while maintaining the Kagome ordering. The pristine surface is thermodynamically stable. Upon creating vacancies, the stability is diminished. In the case of Ge vacancies, the magnetic moment’s ordering remains; however, it is disrupted if Mn vacancies are induced. This is an expected result since Mn vacancies break the triangle like magnetic arrangement that is the fingerprint of Kagome materials. Our results demonstrate that Kagome Mn3Ge surfaces are robust and keep their magnetic properties even with Ge Vacancies. Also, our stability analysis points to a low probability of intrinsic defects or low index reconstructions, making it ideal to look for exchange-biased devices with other ferromagnetic Kagome materials.

Acknowledgments

We thank the projects DGAPA-UNAM IG101124 and IA100624. The calculations were carried out at the supercomputing center UNAM project LANCAD-UNAM-DGTIC-368 and -422, LNS-BUAP project 202201042N, and THUBAT KAAL IPICYT project TKII-JGSA001.