Hybrid Layered Double Perovskite Halides of Transition Metals
2022
Vishnoi, Pratap | Zuo, Julia L. | Li, Xiaotong | Binwal, Devesh Chandra | Wyckoff, Kira E. | Mao, Lingling | Kautzsch, Linus | Wu, Guang | Wilson, Stephen D. | Kanatzidis, Mercouri G. | Seshadri, Ram | Cheetham, A. K.
Hybrid layered double perovskite (HLDP) halides comprise hexacoordinated 1+ and 3+ metals in the octahedral sites within a perovskite layer and organic amine cations between the layers. Progress on such materials has hitherto been limited to compounds containing main group 3+ ions isoelectronic with Pbᴵᴵ (such as Sbᴵᴵᴵ and Biᴵᴵᴵ). Here, we report eight HLDP halides from the A₂MᴵMᴵᴵᴵX₈ family, where A = para-phenylenediammonium (PPDA), 1,4-butanediammonium (1,4-BDA), or 1,3-propanediammonium (1,3-PDA); Mᴵ = Cu or Ag; Mᴵᴵᴵ = Ru or Mo; X = Cl or Br. The optical band gaps, which lie in the range 1.55 to 2.05 eV, are tunable according to the layer composition, but are largely independent of the spacer. Magnetic measurements carried out for (PPDA)₂AgᴵRuᴵᴵᴵCl₈ and (PPDA)₂AgᴵMoᴵᴵᴵCl₈ show no obvious evidence of a magnetic ordering transition. While the t₂g³ Moᴵᴵᴵ compound displays Curie–Weiss behavior for a spin-only d³ ion, the t₂g⁵ Ruᴵᴵᴵ compound displays marked deviations from the Kotani theory.
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