Phase Stability and Magnetic Properties of Compositionally Complex n = 2 Ruddlesden-Popper Perovskites.

Four new compositionally complex perovskites with multiple (four or more) cations on the B site of the perovskites have been studied. The materials have the general formula La 0.5 Sr 2.5 (M) 2 O 7-δ (M = Ti, Mn, Fe, Co, and Ni) and have been synthesized via conventional solid-state synthesis. The compounds are the first reported examples of compositionally complex n = 2 Ruddlesden-Popper perovskites. The structure and properties of the materials have been determined using powder X-ray diffraction, neutron diffraction, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and magnetometry. The materials are isostructural and adopt the archetypal I 4/ mmm space group with the following unit cell parameters: a ∼ 3.84 Å, and c ∼ 20.1 Å. The measured compositions from energy dispersive X-ray spectroscopy were La 0.51(2) Sr 2.57(7) Ti 0.41(2) Mn 0.41(2) Fe 0.39(2) Co 0.38(1) Ni 0.34(1) O 7-δ , La 0.59(4) Sr 2.29(23) Mn 0.58(5) Fe 0.56(6) Co 0.55(6) Ni 0.42(4) O 7-δ , La 0.54(2) Sr 2.49(13) Mn 0.41(2) Fe 0.81(5) Co 0.39(3) Ni 0.36(3) O 7-δ , and La 0.53(4) Sr 2.55(19) Mn 0.67(6) Fe 0.64(5) Co 0.31(2) Ni 0.30(3) O 7-δ . No magnetic contribution is observed in the neutron diffraction data, and magnetometry indicates a spin glass transition at low temperatures.