Solid phases of spatially nanoconfined oxygen: a neutron scattering study

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Understanding the behavior of materials under nanoscale confinement is crucial for developing new technologies.
• Solid oxygen exhibits complex structural and magnetic phase transitions that are sensitive to external conditions.

Purpose of the Study:

• To investigate the structural and magnetic properties of solid oxygen confined within alumina nanochannels.
• To compare the phase behavior of confined oxygen with that of bulk oxygen.
• To explore the influence of confinement on the orientation and ordering of oxygen nanocrystals.

Main Methods:

• Neutron scattering techniques, including elastic scattering and rocking scans.
• Spatial confinement of solid oxygen within 12 nm wide alumina nanochannels.

Main Results:

• The study identified the cubic γ-, orthorhombic β-, and monoclinic α-phases of oxygen within the nanochannels, consistent with bulk behavior.
• Weak antiferromagnetic ordering was observed in the confined monoclinic α-phase.
• Oxygen nanocrystals did not form an isotropic powder, exhibiting preferred orientations influenced by thermal history and transition mechanisms.

Conclusions:

• Confinement in alumina nanochannels preserves the fundamental structural phase sequence of solid oxygen.
• The orientation of oxygen nanocrystals is anisotropic and depends on the thermal history and transition pathways.
• Neutron scattering is effective in probing the structural and magnetic properties of confined systems.