Hole and electron doping of topochemically reduced Ni(I)/Ru(II) insulating ferromagnetic oxides

Journal article

La_xSr_2–xNiRuO₆, La_xSr_4–xNiRuO₈, and La_xSr_3–xNiRuO₇ are, respectively, the n = ∞, 1, and 2 members of the (La_x/2Sr_1–(x/2))_nSr(Ni_0.5Ru_0.5)_nO_3n+1 compositional series. Reaction with CaH₂, in the case of the La_xSr_2–xNiRuO₆ perovskite phases, or Zr oxygen getters in the case of the La_xSr_4–xNiRuO₈ and La_xSr_3–xNiRuO₇ Ruddlesden–Popper phases, yields the corresponding topochemically reduced (La_x/2Sr_1–(x/2))_nSr(Ni_0.5Ru_0.5)_nO_3n–1 compounds (La_xSr_2–xNiRuO₄, La_xSr_4–xNiRuO₆, and La_xSr_3–xNiRuO₅), which contain Ni and Ru cations in square-planar coordination sites. The x = 1 members of each series (LaSrNiRuO₄, LaSr₃NiRuO₆, and LaSr₂NiRuO₅) exhibit insulating ferromagnetic behavior at low temperature, attributable to exchange couplings between the Ni¹⁺ and Ru²⁺ centers they contain. Increasing the La³⁺ concentration (x > 1) leads to a reduction of some of the Ru²⁺ centers to Ru¹⁺ centers and a suppression of the ferromagnetic state (lower T_c, reduced saturated ferromagnet moment). In contrast, increasing the Sr²⁺ concentration (x < 1) oxidizes some of the Ru²⁺ centers to Ru³⁺ centers and enhances the ferromagnetic coupling (increased T_c, increased saturated ferromagnet moment) for the n = ∞ and n = 2 samples but appears to have no influence on the magnetic ordering temperature of the n = 1 samples. The magnetic couplings and influence of doping are discussed on the basis of superexchange and direct exchange couplings between the square-planar Ni and Ru centers.

Authors: Xu, Z; Jin, L; Backhaus, J-K; Green, F; Hayward, MA

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Chemical Society
• Journal: Inorganic Chemistry
• Volume: 60
• Issue: 19
• Pages: 14904-14912
• Place of publication: United States
• Publication date: 2021-09-13
• Acceptance date: 2021-08-31
• DOI: 10.1021/acs.inorgchem.1c02265
• EISSN: 1520-510X
• ISSN: 0020-1669
• Pmid: 34516081
• Language: English
• Keywords: FFR