Depopulation of the Mn2+ 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+ → 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.

MnBi2Te4/(Bi2Te3)n materials system has recently generated strong interest as a natural platform for realization of the quantum anomalous Hall (QAH) state. The system is magnetically much better ordered than substitutionally doped materials, however, the detrimental effects of certain disorders are becoming increasingly acknowledged. Here, from compiling structural, compositional, and magnetic metrics of disorder in ferromagnetic MnBi2Te4/(Bi2Te3)n it is found that migration of Mn between MnBi2Te4 septuple layers (SLs) and otherwise non-magnetic Bi2Te3 quintuple layers (QLs) has systemic consequences - it induces ferromagnetic coupling of Mn-depleted SLs with Mn-doped QLs, seen in ferromagnetic resonance as an acoustic and optical resonance mode of the two coupled spin subsystems. Even for a large SL separation (n ≳ 4 QLs) the structure cannot be considered as a stack of uncoupled two-dimensional layers. Angle-resolved photoemission spectroscopy and density functional theory studies show that Mn disorder within an SL causes delocalization of electron wave functions and a change of the surface band structure as compared to the ideal MnBi2Te4/(Bi2Te3)n. These findings highlight the critical importance of inter- and intra-SL disorder towards achieving new QAH platforms as well as exploring novel axion physics in intrinsic topological magnets.

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A single crystal of (Pb,Cd)Te solid solution with Cd content equal to 5% was grown by self-selecting vapour growth technique and characterized by powder X-ray diffraction using the X'Pert PANalytical diffractometer and Cu Kα 1 radiation. The X-ray diffraction pattern refinement demonstrated the fcc structure of the rock-salt type of investigated sample, no precipitates or other crystal phases were detected. The sample chemical composition was determined on the basis of measured lattice parameter value. Next, the Young modulus and microhardness were determined by the nanoindentation for carefully prepared, (001), (011) and (111)-oriented single crystal plates. The slight anisotropy of two parameters mentioned above has been found and compared with available literature data.