Materials displaying anomalous physical properties have recently attracted scientific interest because they could be potentially used in future spintronic and electronic devices. In this context Mn₅Si₃ and Mn₅Ge₃ are promising candidate materials for applications since they exhibit significant anomalous Hall and Nerst effects [1-3]. Although the crystal structure, the magnetic structure, and the macroscopic properties of these materials were extensively investigated in the past their spin excitation spectrum remained unexplored. In this seminar I will present recent results of inelastic neutron scattering measurements and density functional theory calculations [4-7]. Our studies indicate that the non-collinear magnetic ground state of Mn₅Si₃ and its modification via external magnetic field is associated with the anomalous transport properties and the interesting thermodynamic phenomena that occur in this material [5,6]. Regarding the ferromagnetic Mn₅Ge₃ our results demonstrate that this compound is the first realization of a gapped Dirac magnon material in three dimensions [7]. Its tunability by chemical doping or by thin film nanostructuring could define an exciting new platform to explore and design topological magnons for applications.

[1] C. Sürgers et al., Nature Communications 5, 3400 (2014).
[2] Changgan Zeng et al., Phys. Rev. Lett. 96, 037204 (2006).
[3] R. Kraft et al., J Appl Phys 128, 033905 (2020).
[4] F.J. dos Santos et al., Phys. Rev. B 103, 024407 (2021).
[5] N. Biniskos et al., Physical Review Letters 120, 257205 (2018).
[6] N. Biniskos et al., Phys. Rev. B 105, 104404 (2022).
[7] Topological magnons driven by the Dzyaloshinskii-Moriya interaction in the centrosymmetric ferromagnet Mn5Ge3, arXiv:2211.16925