Altermagnetism explored in MnTe and Mn5Si3 thin films

CIC nanoGUNE Seminars

Prof. Helena Reichlovaa
Technische Universität Dresden, Germany & Czech Academy of Sciences, Czech Republic
nanoGUNE seminar room, Tolosa Hiribidea 76, Donostia - San Sebastian
F. Casanova
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Altermagnetism explored in MnTe and Mn5Si3 thin films

The experimental work presented in this talk has been inspired by theoretical predictions that the time-reversal symmetry breaking electronic structure and responses can occur within an abundant family of materials with a compensated collinear magnetic order [1,2]. The key characteristic feature is an alternating spin polarization in both real-space crystal structure and momentum-space electronic structure, which has suggested to term this emerging phase altermagnetism [3].

Anomalous Hall effect is a prime example of electronic responses commonly associated with the spontaneous time-reversal symmetry breaking in the electronic structure of ferromagnets and we use as a tool to identify the altermagnetic phase. I will first present our experimental observation of a spontaneous anomalous Hall response in the absence of an external magnetic field in an epitaxial film of MnTe, which is a semiconductor with a collinear antiparallel magnetic ordering of Mn moments [4]. The anisotropic crystal environment of magnetic Mn atoms due to the non-magnetic Te atoms is essential for establishing the altermagnetic phase. In the second part of the talk, I will present our observation of the spontaneous anomalous Hall effect in epitaxial thin-film Mn5Si3 [5]. We have studied Mn5Si3 epilayers grown on Si(111) substrate. We observe that epitaxial constraints stabilize a hexagonal unit cell in the magnetic state distinct from previously described phases in bulk Mn5Si3 crystals [8]. We observe a sizable spontaneous anomalous Hall conductivity of 5-20 S/cm, accompanied by a negligible net magnetization. In the last part of the talk, I will mention our ongoing projects and possible future directions to exploit altermagnetic properties.

[1] Smejkal et al. Science Advances 6, 23 (2020)
[2] Mazin et al. PNAS 118 42 (2021)
[3] Smejkal et al., Phys. Rev. X 12 040501 (2022)
[4] Gonzalez-Betancourt, Phys. Rev. Lett. 130, 036702 (2023)
[5] Reichlova et al., arXiv:2012.15651