Pressure pushes Y-kapellasite into a fluctuating magnetic state
A team including researchers from the Max Planck Institute for Solid State Research has shown that hydrostatic pressure can drive the kagome magnet Y-kapellasite, Y3Cu9(OH)19Cl8, from long-range magnetic order into a fully dynamical, spin-liquid-like state. The work was published in Physical Review Letters and selected as an Editors’ Suggestion, highlighting its broader relevance for quantum materials research.
Y-kapellasite is a particularly attractive system because it is a structurally clean kagome antiferromagnet. At ambient pressure, its distorted kagome lattice partially relieves frustration and allows magnetic order to emerge below about 2.2 K. At the same time, earlier work had placed the material close to a phase boundary to a spin-liquid regime. This makes it an ideal platform for a central question in frustrated magnetism: can magnetic order be suppressed by tuning frustration alone, without introducing disorder? The new study shows that this is indeed possible. Using muon spin rotation under hydrostatic pressure, the researchers found that the static magnetism present at ambient pressure disappears completely by 2.3 GPa. Instead, the spins remain dynamic down to the lowest measured temperatures, with no sign of spin freezing. Complementary high-pressure x-ray diffraction and infrared spectroscopy show that this change is not driven by a structural phase transition. Rather, pressure gradually reduces the anisotropy of the kagome lattice, increases magnetic frustration, and leaves the Cu–O framework essentially intact.
This is what makes the result so important. In many candidate quantum spin liquids, disorder complicates the interpretation because it can imitate some of the same experimental signatures. In Y-kapellasite, by contrast, the fluctuating state emerges in clean single crystals under a controlled external tuning parameter. The study therefore establishes Y-kapellasite as a rare model system in which long-range order is suppressed by pressure-tuned frustration, providing a particularly promising route toward a quantum spin liquid without strong disorder.
