Spatial and Temporal Correlations of XY Macro Spins

Area of Science:

• Condensed Matter Physics
• Materials Science
• Magnetism

Background:

• Investigating magnetic phases and spin correlations in nanoscale systems is crucial for understanding emergent magnetic phenomena.
• The 'order-by-disorder' mechanism, a theoretical prediction from 30 years ago, requires experimental validation in controlled systems.

Purpose of the Study:

• To experimentally probe magnetic ground states and spin correlations in micro-scale XY dipolar systems using nano disk arrays.
• To investigate the 'order-by-disorder' phenomenon and characterize magnetic phases in square and honeycomb lattice symmetries.

Main Methods:

• Fabrication of nano disk arrays with square and honeycomb symmetries.
• Utilizing magnetization-sensitive X-ray photoemission electron microscopy (XPEEM) for probing magnetic states at the micro scale.

Main Results:

• Observed an antiferromagnetic striped ground state in square lattices.
• Identified 6-fold symmetric structures, including trigonal vortex lattices and disordered floating vortices, in honeycomb lattices.
• Characterized a phase transition in the honeycomb lattice driven by spin frustration, transitioning from long-range order to a Berezinskii-Thouless-Kosterlitz-like phase and finally to a paramagnetic state.

Conclusions:

• The 'order-by-disorder' phenomenon is experimentally observed in these micro-scale magnetic systems.
• Spin frustration in honeycomb lattices leads to complex magnetic phases and vortex dynamics, suggesting degeneracy of vortex circulation.