Oxygen-driven competition between low-dimensional structures of Sr3CoMO6 and Sr3CoMO7-δ with M = Ru, Ir

Area of Science:

• Materials Science
• Solid-State Chemistry
• Crystallography

Background:

• The study focuses on layered perovskite oxides, specifically cobalt-containing compounds.
• Understanding structure-property relationships in these materials is crucial for potential applications.

Purpose of the Study:

• To investigate the reversible structural transformation of 1D Sr3CoMO6 to 2D Sr3CoMO7-δ.
• To explore the impact of oxygen partial pressure on cation ordering and oxidation states.
• To analyze the magnetic behavior of the parent and transformed compounds.

Main Methods:

• Synthesis of 1D Sr3CoMO6 and 2D Sr3CoMO7-δ compounds (M = Ru, Ir).
• X-ray absorption spectroscopy (soft and hard) to probe cation oxidation states and local structure.
• Magnetic susceptibility measurements to determine magnetic ordering and behavior.

Main Results:

• A reversible transformation from 1D K4CdCl6-type (Sr3CoMO6) to 2D Ruddlesden-Popper (Sr3CoMO7-δ) structure was achieved by increasing oxygen pressure.
• Cations (Co and M) were oxidized from Co(2+)/M(4+) to Co(3+)/M(5+).
• High-spin Co(2+) transformed to high-spin Co(3+) and then to low-spin Co(3+) with increasing oxygen pressure.
• 1D compounds exhibited axial magnetic ordering, while 2D compounds showed spin-glass-like behavior due to cation disorder.

Conclusions:

• The structural and electronic properties of Sr3CoMO6 can be tuned by controlling oxygen partial pressure.
• The observed magnetic transitions are directly linked to the structural transformation and cation oxidation states.
• These findings offer insights into the design of functional layered oxide materials.