Evidence for an exotic magnetic transition in the triangular spin system FeGa2S4

TL;DR

This study reveals a previously undetected magnetic transition in FeGa2S4 at 30 K using muon spin relaxation, indicating an exotic magnetic state distinct from conventional phases and different from similar systems like NiGa2S4.

Contribution

The paper reports the discovery of a new magnetic transition in FeGa2S4 using muon spin relaxation, highlighting an exotic magnetic state not seen in prior measurements.

Findings

Detected a magnetic transition at T* ≈ 30 K.

Persistent spin dynamics observed down to 0.1 K.

Transition likely differs from the Z_2 topological transition in NiGa2S4.

Abstract

We report positive muon spin relaxation measurements on the triangular lattice magnetic system FeGa2S4. A magnetic transition not previously detected by specific heat and magnetic susceptibility measurements is found in zero field at T^* \simeq 30 K. It is observed through the temperature dependencies of the signal amplitude and the spin-lattice relaxation rate. This transition is therefore not a conventional magnetic phase transition. Since persistent spin dynamics is observed down to 0.1 K, the ground state cannot be of the canonical spin-glass type, which could be suggested from hysteresis effects in the bulk susceptibility below T_f \simeq 16 K. These results are compared to those found for the isomorph NiGa2S4. It is argued that the fate of the transition, which has been interpreted in terms of the Z_2 topological transition in this latter system, is probably different in FeGa2S4.