arXiv subjects

P. Skupiński

Publications and source records attributed to P. Skupiński.

4 recordsLinked to original sources

arXiv2025

Antiferromagnetic resonance in $α$-MnTe

Antiferromagnetic resonance in a bulk $α$-MnTe crystal is investigated using both frequency-domain and time-domain THz spectroscopy techniques. At low temperatures, an excitation at the photon energy of $(3.5\pm 0.1)$~meV is observed and identified as a magnon mode through its distinctive dependence on temperature and magnetic field. This behavior is reproduced using a simplified model for antiferromagnetic resonance in an easy-plane antiferromagnet. The results of our experiments, when compared to exchange constants established in the literature, allow us to extract the out-of-plane component of the single-ion magnetic anisotropy reaching $(40\pm10)$~$μ$eV.

cond-mat.mtrl-sci↗

arXiv2023

Coexistence of Anomalous Hall Effect and Weak Net Magnetization in Collinear Antiferromagnet MnTe

Anomalous Hall effect (AHE) plays important role in the rapidly developing field of antiferromagnetic spintronics. It has been recently discussed that it can be a feature of not only uncompensated magnetic systems but also in altermagnetic materials. Hexagonal MnTe belongs to this appealing group of compounds exhibiting AHE and is commonly perceived as magnetically compensated. Here, we demonstrate that bulk form of MnTe exhibits small but detectable magnetic moment correlating with hysteretic behaviour of the AHE. We formulate a phenomenological model which explains how this feature allows to create a disbalance between states with opposite Néel vector and prevent the AHE signal from averaging out to zero. Moreover, we show how the dependence of AHE on the Néel vector arises on microscopical level and highlight the differences in Berry curvature between magnetically compensated and uncompensated systems.

cond-mat.mes-hall↗

arXiv2023

Fermi level dependence of magnetism and magnetotransport in the magnetic topological insulators Bi$_{2}$Te$_{3}$ and BiSbTe$_{3}$ containing self-organized MnBi$_{2}$Te$_{4}$ septuple layers

The magnetic coupling mechanisms underlying ferromagnetism and magnetotransport phenomena in magnetically doped topological insulators have been a central issue to gain controlled access to the magneto-topological phenomena such as quantum anomalous Hall effect and topological axion insulating state. Here, we focus on the role of bulk carriers in magnetism of the family of magnetic topological insulators, in which the host material is either Bi$_{2}$Te$_{3}$ or BiSbTe$_{3}$, containing Mn self-organized in MnBi$_{2}$Te$_{4}$ septuple layers. We tune the Fermi level using the electron irradiation technique and study how magnetic properties vary through the change in carrier density, the role of the irradiation defects is also discussed. Ferromagnetic resonance spectroscopy and magnetotransport measurements show no effect of the Fermi level position on the magnetic anisotropy field and the Curie temperature, respectively, excluding bulk magnetism based on a carrier-mediated process. Furthermore, the magnetotransport measurements show that the anomalous Hall effect is dominated by the intrinsic and dissipationless Berry-phase driven mechanism, with the Hall resistivity enhanced near the bottom/top of the conduction/valence band, due to the Berry curvature which is concentrated near the avoided band crossings. These results demonstrate that the anomalous Hall effect can be effectively managed, maximized, or turned off, by adjusting the Fermi level.

cond-mat.mtrl-sci↗

arXiv2016

Metastability of Mn$^{3+}$ in ZnO driven by strong $d$(Mn) intrashell Coulomb repulsion: experiment and theory

Depopulation of the Mn$^{2+}$ state in ZnO:Mn upon illumination, monitored by quenching of the Mn$^{2+}$ EPR signal intensity, was observed at temperatures below 80~K. Mn$^{2+}$ photoquenching is shown to result from the Mn$^{2+}$ $\to$ Mn$^{3+}$ ionization transition, promoting one electron to the conduction band. Temperature dependence of this process indicates the existence of an energy barrier for electron recapture of the order of 1~meV. GGA$+U$ calculations show that after ionization of Mn$^{2+}$ a moderate breathing lattice relaxation in the 3+ charge state occurs, which increases energies of $d$(Mn) levels. At its equilibrium atomic configuration, Mn$^{3+}$ is metastable since the direct capture of photo-electron is not possible. The metastability is mainly driven by the strong intra-shell Coulomb repulsion between $d$(Mn) electrons. Both the estimated barrier for electron capture and the photoionization energy are in good agreement with the experimental values.

cond-mat.mtrl-sci↗