Magnetization Density Distribution of Sr_{2}IrO_{4}: Deviation from a Local j_{eff}=1/2 Picture.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• 5d iridium oxides exhibit strong spin-orbit coupling, driving interest in novel quantum states.
• Strontium iridate (Sr_{2}IrO_{4}) is a key material featuring a j_{eff}=1/2 state, crucial for unconventional Mott insulating behavior.

Purpose of the Study:

• To investigate the detailed magnetization density distribution in Sr_{2}IrO_{4} under an applied magnetic field.
• To assess the validity of the simplified j_{eff}=1/2 model in describing the electronic and magnetic properties of Sr_{2}IrO_{4}.

Main Methods:

• Polarized neutron diffraction was employed to measure the magnetization density.
• The data was analyzed using maximum entropy method and multipole expansion model refinement.

Main Results:

• An anisotropic and aspherical magnetization density distribution was observed, deviating significantly from the j_{eff}=1/2 picture.
• The reconstructed magnetization density features prominent cross-shaped positive lobes along crystallographic axes, indicating a dominant xy orbital contribution.
• These findings persist even when accounting for distortions affecting orbital populations.

Conclusions:

• The electronic structure of Sr_{2}IrO_{4} is more complex than the simplest j_{eff}=1/2 model suggests.
• The observed magnetization density distribution challenges conventional interpretations and may imply a weaker analogy to superconducting copper oxides.