Strongly frustrated 2D magnetism in a 3D hexagonal perovskite

Original · EN

Exotic quantum phenomena are often found to occur in spin systems that exhibit low-dimensional magnetism. By combining nuclear magnetic resonance, neutron scattering, and muon-spin spectroscopy (μSR) techniques, we report a rare instance of strongly frustrated two-dimensional (2D) magnetism in a three-dimensional (3D) hexagonal perovskite. Here, Ba₂La₂MnTe₂O₁₂, a triangular-lattice magnet, is shown to undergo a magnetic transition at Tₙ ≈ 4.4 K, below which the manganese moments form a 120∘ AFM order within the ab-plane, while staying disordered along the c-axis. This exotic ground state, which exhibits ideal 2D magnetism, is highly consistent with the persistently strong spin fluctuations and the large internal field distributions revealed by zero-field μSR. Further, the 2D magnetism also leads to a significant frustration, much larger than that of most known magnetically-ordered frustrated systems. Our work on Ba₂La₂MnTe₂O₁₂ not only challenges the interpretations of magnetic order in other 3D hexagonal perovskites, but it also provides insight into how the dimensionality affects the exotic magnetic states.