On-line SPICE-SPIN+X Seminars

On-line Seminar: 08.06.2022 - 15:00 German Time

Spontaneous anomalous Hall response and altermagnetism explored in MnTe and Mn5Si3

Helena Reichlova, TU Dresden

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. More recently, the anomalous Hall effect and other time-reversal symmetry breaking responses were also theoretically and experimentally established in crystals with a vanishing net magnetization and a non-collinear magnetic order [1,2]. 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 [2-4]. The underlying unconventional magnetic phase forms in crystals whose opposite-spin sublattices are connected by a rotation symmetry-transformation [5]. Its 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 [5].

We 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 [6]. The anisotropic crystal environment of magnetic Mn atoms due to the non-magnetic Te atoms is essential for establishing the unconventional phase and generating the anomalous Hall effect in MnTe [5,6]. In the second part of the talk, we will present our observation of the spontaneous anomalous Hall effect in epitaxial thin-film Mn5Si3 [7]. 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. Combined with the theoretical symmetry analysis and microscopic ab initio calculations, we conclude that our thin-film Mn5Si3 is a candidate for a d-wave form of the altermagnetic phase, generated by a compensated collinear ordering of magnetic moments on the lattice of Mn atoms [4,6].

[1] Nakatsuji and Arita, Annual Review of CMP 13, 119-142 (2022)
[2] Smejkal et al. Nat. Rev. Mater., on-line 30 March (2022)
[3] Smejkal et al. Science Advances 6, 23 (2020)
[4] Mazin et al. PNAS 118 42 (2021)
[5] Smejkal et al. arXiv:2105.05820, arXiv:2204.10844
[6] Gonzales-Betancourt et al. arXiv:2112.06805
[7] Reichlova et al., arXiv:2012.15651
[8] Gottschilch et al., J. Mater. Chem., 22, 15275 (2012)

Please sign up here in order to get the Zoom link and regular announcements of the upcoming talks.
PDF file of the talk available here