UT Austin Researchers Uncover Exotic Magnetic Phases, Realizing Decades-Old Theory
Researchers at The University of Texas at Austin have experimentally demonstrated a sequence of exotic magnetic phases in an ultrathin material, fully realizing a theoretical model of two-dimensional magnetism proposed in the 1970s. The groundbreaking findings, published in Nature Materials, involved a material called nickel phosphorus trisulfide (NiPS₃).
Key Discoveries: A Tale of Two Magnetic Phases
As an atomically thin sheet of NiPS₃ was cooled, two distinct magnetic phases were observed:
- Berezinskii–Kosterlitz–Thouless (BKT) phase: Between –150 and –130 °C, the material formed swirling patterns of magnetic moments called vortices, where pairs wound in opposite directions and remained tightly bound.
- Six-state clock ordered phase: Upon further cooling, the material transitioned into this phase, where magnetic moments adopted one of six symmetry-related orientations.
These observations represent the first time both transitions have been seen together in a complete sequence, establishing the experimental realization of the two-dimensional six-state clock model.
Significance and Future Impact
Edoardo Baldini, assistant professor of physics at UT and research leader, stated that the BKT phase's robust, nanoscale vortices offer a new method for controlling magnetism at the nanoscale and provide insight into universal topological physics in two-dimensional systems.
The research suggests potential for inspiring new, ultracompact technologies and indicates that a broad range of two-dimensional magnetic materials may contain previously unexplored phases.
Future work aims to stabilize similar magnetic phases at higher temperatures, potentially reaching room temperature.