Unconventional spin freezing and fluctuations in the frustrated antiferromagnet NiGa2S4

Abstract

Muon spin rotation (muSR) experiments reveal unconventional spin freezing and dynamics in the two-dimensional (2D) triangular lattice antiferromagnet NiGa2S4. Long-lived disordered Ni-spin freezing (correlation time > 10-6 s at 2 K) sets in below T_f = 8.5 +- 0.5 K with a mean-field-like temperature dependence. The observed exponential temperature dependence of the muon spin relaxation above T_f is strong evidence for 2D critical spin fluctuations. Slow Ni spin fluctuations coexist with quasistatic magnetism at low temperatures but are rapidly suppressed for fields > 10 mT, in marked contrast with the field-independent specific heat. The muSR and bulk susceptibility data indicate a well-defined 2D phase transition at T_f, below which NiGa2S4 is neither a conventional magnet nor a singlet spin liquid.

5 pages, 4 figures, to be published in Phys. Rev. B

References in corpus (6)

• The quadrupolar phases of the S=1 bilinear-biquadratic Heisenberg model on the triangular lattice
• Unconventional Dynamics in Triangular Heisenberg Antiferromagnet NaCrO2
• Magnetic density of states at low energy in geometrically frustrated systems
• Spin dynamics and spin freezing behavior in the two-dimensional antiferromagnet NiGa${}_2$S${}_4$ revealed by Ga-NMR, NQR and $\mu$SR measurements
• Vortex-induced topological transition of the bilinear-biquadratic Heisenberg antiferromagnet on the triangular lattice
• Short-range magnetic ordering process for the triangular lattice compound NiGa2S4: a positive muon spin rotation and relaxation study

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• Evidence for an exotic magnetic transition in the triangular spin system FeGa2S4
• Magnetic ordering and spin dynamics in $S=5/2$ staggered triangular lattice antiferromagnet Ba${}_2$MnTeO${}_6$
• Phase diagram of a bilinear-biquadratic spin-1 model on the triangular lattice from density matrix renormalization group simulations
• Observation of topological $Z_2$ vortex fluctuations in the frustrated Heisenberg magnet NaCrO${}_2$
• Gapless spinon excitations emerging from a multipolar transverse field in the triangular-lattice Ising antiferromagnet NaTmSe2
• Unusual spin dynamics in the van der Waals antiferromagnet FeGa2S4
• Weak-coupling Mean-field Theory of Magnetic Properties of NiGa${}_2$S${}_4$