Dresden 2026 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 13: Magnetic Heuslers and Semiconductors

MA 13.8: Vortrag

Montag, 9. März 2026, 16:45–17:00, POT/0361

Fe³⁺-Centers as Structural Probes in Fe-Doped Cs₂AgBiBr₆ Semiconducting Perovskite — •Volodymyr Vasylkovskyi¹, Timur Biktagirov², Anastasiia Kultaeva¹, Carlos Canhassi³, Mykola Slipchenko⁴, Yakov Kopelevich³, and Vladimir Dyakonov¹ — ¹Experimental Physics 6, University of Würzburg, 97074 Würzburg, Germany — ²Physics Department, Paderborn University, D-33098 Paderborn, Germany — ³Gleb Wataghin Institute of Physics, University of Campinas, 13083-859 Campinas, Brazil — ⁴Institute for Scintillation Materials, Kharkiv, Ukraine

Fe-doping introduces new functionality into halide double perovskites alongside modifying optical properties. We report controlled growth of Fe-doped Cs₂AgBiBr₆ single crystals and correlate their structural, optical, and magnetic parameters. ICP analysis confirms Fe incorporation below 0.1% relative to Bi, which induce defect-related sub-gap absorption and photoluminescence shift. EPR measurements reveal an S = 5/2 Fe³⁺ spin center whose anisotropy follows the phase transition below 120 K. DFT calculations, guided by angular-dependent EPR, identify these centers as impurity-vacancy complexes, likely Fe_Bi-V_Br. SQUID magnetometry shows ferromagnetic-type hysteresis at room temperature, with rising spontaneous magnetization below 20-30 K and magnetization irreversibility under zero-field and field-cooling, confirming ferromagnetism from Fe-related defect complexes. Even small Fe amounts significantly alter optical and magnetic behavior of Cs₂AgBiBr₆, emphasizing the role of controlled doping and defect engineering in lead-free double perovskites.

Keywords: Cs$_2$AgBiBr$_6$; Crystal growth; Perovskite; Iron; Defects