CoVO₃ High-Pressure Polymorphs: To Order or Not to Order?

Area of Science:

• Solid State Chemistry
• Materials Science
• Condensed Matter Physics

Background:

• Material properties are dictated by composition and structure.
• ABO3 oxides exhibit diverse physical properties based on cation ordering, forming perovskite or corundum derivatives.
• Materials existing in multiple structural forms offer unique insights into structure-property relationships.

Purpose of the Study:

• To investigate the structural and magnetic properties of cobalt vanadate (CoVO3) polymorphs.
• To explore the influence of pressure on the structural modifications and resulting magnetic behaviors of CoVO3.
• To understand the role of vanadium in the magnetic properties of CoVO3-I and the magnetic frustration in CoVO3-II.

Main Methods:

• Synthesis of CoVO3 in two polymorphs (CoVO3-I and CoVO3-II) at moderate (8-12 GPa) and high pressures (22 GPa), respectively.
• Characterization of structural and magnetic properties of the synthesized polymorphs.
• First-principles calculations to elucidate the electronic and magnetic interactions.

Main Results:

• CoVO3-I exhibits a honeycomb zigzag magnetic structure in the cobalt network, with vanadium playing a crucial role.
• CoVO3-II displays cluster-glass magnetic behavior due to two independent interpenetrating antiferromagnetic Co- and ferromagnetic V-hcp sublattices, causing magnetic frustration.
• CoVO3-II is the first oxide with the LiNbO3-type structure containing both Co and V with free d electrons.

Conclusions:

• The cation distribution in CoVO3 polymorphs significantly impacts their magnetic properties.
• Vanadium's influence is critical for the magnetic behavior of CoVO3-I, contrary to previous assumptions.
• The CoVO3 polymorphs highlight a broader phase field for high-pressure A-site cobaltites.