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K₂Ni₂(SO₄)₃ is a three dimensional frustrated antiferromagnet in which Ni²⁺(S = 1) ions occupy two interpenetrating trillium sublattices that together form a unique tetra-trillium network. Recent thermodynamic, inelastic neutron scattering, and muon spin relaxation (μSR) studies show that, at ambient pressure and zero magnetic field, K₂Ni₂(SO₄)₃ hosts a highly dynamic, correlated ground state with features reminiscent of a quantum spin liquid (QSL), coexisting with a very small static ordered component — behavior that places the system close to a quantum critical regime [1-3]
To investigate how this dynamic state evolves when magnetic interactions are tuned, we performed detailed μSR experiments on K₂Ni₂(SO₄)₃ under hydrostatic pressure up to 23 kbar. At low pressures (below about 8.6 kbar), the ZF-μSR spectra measured at millikelvin temperatures show predominantly dynamic relaxation, consistent with persistent spin fluctuations. At and above approximately 9.5 kbar, pronounced oscillations appear in the ZF μSR time spectra, providing clear evidence for the development of static internal magnetic fields and indicating that pressure drives the system toward a more static, magnetically ordered regime. The evolution of the internal field strength with pressure and temperature highlights a systematic suppression of spin fluctuations and increasing stabilization of static correlations under compression.
These results demonstrate that hydrostatic pressure is a powerful tuning parameter in K₂Ni₂(SO₄)₃, transforming the magnetic ground state from a dynamic, frustration dominated regime toward static magnetism. This behavior underscores the sensitivity of three dimensional frustrated spin networks to small perturbations and establishes pressure as a promising route for exploring competing quantum phases and proximate QSL behavior in 3D frustrated magnets.
[1] I. Živković et al., Phys. Rev. Lett 127, 157204 (2021).
[2] M. G. Gonzalez et al., Nat. Commun. 15, 7191 (2024).
[3] W. Yao et al., Phys. Rev. Lett 131, 146701 (2023).