Ba₄RuMn₂O₁₀: A Noncentrosymmetric Polar Crystal Structure with Disordered Trimers

Area of Science:

• Solid State Chemistry
• Materials Science
• Crystallography

Background:

• Understanding the relationship between crystal structure and physical properties is crucial for designing new materials.
• Exploring complex oxide materials can lead to novel electronic and magnetic functionalities.

Purpose of the Study:

• To synthesize and characterize a new polar material, Ba4RuMn2O10.
• To determine its crystal structure and investigate its magnetic and electronic properties.

Main Methods:

• Powder neutron diffraction with Rietveld refinement
• Second harmonic generation (SHG)
• Convergent beam electron diffraction (CBED)
• X-ray absorption near-edge spectroscopy (XANES)

Main Results:

• Phase-pure Ba4RuMn2O10 was successfully synthesized, adopting a noncentrosymmetric polar crystal structure (space group Cmc21).
• The structure features zigzag chains of corner-shared trimers with disordered Ru/Mn occupations at three distinct metal sites.
• The material exhibits a narrow bandgap (approx. 0.6 eV) and displays spin-glass behavior with antiferromagnetic interactions.

Conclusions:

• The disordered distribution of Ru and Mn ions lowers the symmetry, inducing a polar crystal structure.
• Ba4RuMn2O10 is a narrow bandgap semiconductor with complex magnetic properties, including spin-glass behavior and magnetic frustration.