Lawrence Berkeley National Laboratory
Spatial and Temporal Correlations of XY Macro Spins.
- Author(s): Streubel, Robert
- Kent, Noah
- Dhuey, Scott
- Scholl, Andreas
- Kevan, Steve
- Fischer, Peter
- et al.
Published Web Locationhttps://doi.org/10.1021/acs.nanolett.8b01789
We use nano disk arrays with square and honeycomb symmetry to investigate magnetic phases and spin correlations of XY dipolar systems at the micro scale. Utilizing magnetization sensitive X-ray photoemission electron microscopy, we probe magnetic ground states and the "order-by-disorder" phenomenon predicted 30 years ago. We observe the antiferromagnetic striped ground state in square lattices, and 6-fold symmetric structures, including trigonal vortex lattices and disordered floating vortices, in the honeycomb lattice. The spin frustration in the honeycomb lattice causes a phase transition from a long-range ordered locked phase over a floating phase with quasi long-range order and indications of a Berezinskii-Thouless-Kosterlitz-like character, to the thermally excited paramagnetic state. Absent spatial correlation and quasi periodic switching of isolated vortices in the quasi long-range ordered phase suggest a degeneracy of the vortex circulation.