Greifswald 2024 – wissenschaftliches Programm
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SYEC: Symposium Lasers and Photonic Technologies for Environmental Challenges
SYEC 4: Photonics-Assisted Green Energy Production II
SYEC 4.3: Vortrag
Dienstag, 27. Februar 2024, 17:00–17:15, ELP 6: HS 4
Search for ferromagnetism in Mn-doped lead halide perovskites — •Maryam Sajedi1, Chen Luo1, Konrad Siemensmeyer1, Maxim Krivenkov1, Kai Chen1,2, James M. Taylor1,3, Marion A. Flatken1, Florin Radu1, and Oliver Rader1 — 1Helmholz-Zentrum Berlin für Materialien und Energie — 2National Synchrotron Radiation Laboratory, university of Science and Technology of China, — 3Fakultät für Physik, Technische Universität München,
Lead halide perovskites are new key materials in various application areas such as high efficiency photovoltaics, lighting, and photodetectors. Doping with Mn, which is known to enhance the stability, has recently been reported to lead to ferromagnetism below 25 K in methylammonium lead iodide (MAPbI3) mediated by superexchange. Two most recent reports confirm ferromagnetism up to room temperature but mediated by double exchange between Mn2+ and Mn3+ ions. Here we investigate a wide concentration range of MAMnxPb1*xI3 and Mn-doped triple-cation thin films by soft X-ray absorption, X-ray magnetic circular dichroism, and quantum interference device magnetometry. The X-ray absorption lineshape shows clearly an almost pure Mn2+ configuration, confirmed by a sum-rule analysis of the dichroism spectra. A remanent magnetization is not observed down to 2 K. Curie-Weiss fits to the magnetization yield negative Curie temperatures. All data show consistently that significant double exchange and ferromagnetism do not occur. Our results show that Mn is not suitable for creating ferromagnetism in lead halide perovskites.
Keywords: ferromagnetism; perovskites; superexchange; X-ray absorption; X-ray magnetic circular dichroism