Investigation of Faraday Rotation Effect in Solution Grown Perovskite Single Crystals

Abstract

In this report, Faraday rotation effect in the organic/inorganic perovskite single crystals is investigated. Eight halide-based perovskite single crystals with cations of methylammonium (MA), formamidinium (FA), and caesium (Cs) are grown at low temperature via a modified solvent evaporation method or an inverse temperature crystallization technique. The perovskite crystals are examined using single crystal and powder X-ray diffraction techniques, and optical spectroscopy to ensure their pure single crystal phase, high crystallinity, and morphology. Among the eight single crystals investigated, only the MAPbCl3 and MAPbBr3 crystals display Faraday rotation effect in a broad visible range. An optimum rotation angle of nearly 100 degree with a Verdet constant of approximately 450 rad (T•m)−1 is achieved for the MAPbCl3 crystal. Superconducting quantum interference device (SQUID) measurements conducted at room temperature show diamagnetic behavior of all crystals. Moreover, contaminations from magnetic elements (rare earth elements, transition metals, lanthanides, etc.), which could possibly induce magnetic anisotropy, are excluded from the secondary-ion mass spectrometry (SIMS) results. Results from all conducted experiments clearly indicate that the spin-orbital coupling of the lead ion is unlikely responsible for the observed Faraday rotation effect. The combined effects of the proton orbital-orbital interactions in the CH3NH3 (MA) cation under optical field and confinement of the unit cell is proposed as the underlying mechanism for the observed magnetic anisotropy.

Keywords: perovskite single crystal, Faraday rotation, Verdet constant, proton orbital-orbital interaction, spin-orbital coupling, magnetic anisotropy