Spin freezing in the van der Waals material Mn_(2)Ga_(2)S_(5)

摘要

Geometrical frustration in low-dimensional magnetic systems has been an intriguing research aspect,where the suppression of conventional magnetic order may lead to exotic ground states such as spin glass or spin liquid.In this work we report the synthesis and magnetism study of the monocrystalline Mn_(2)Ga_(2)S_(5),featuring both the van derWaals structure and a bilayered triangular Mn lattice.Magnetic susceptibility reveals a significant antiferromagnetic interaction with a Curie-Weiss temperature θ_(w)~-260 K and a high spin S=5/2 Mn^(2+) state.However,no long range magnetic order has been found down to 2 K,and a spin freezing transition is found to occur at around 12 K well below its θ_(w).This yields a frustration index of f=-θ_(w)/T_(f)≈22,an indication that the system is highly frustrated.The absence of a double-peak structure in magnetic specific heat compared with the TM_(2)S_(4) compounds implies that the spin freezing behavior in Mn_(2)Ga_(2)S_(5)is a result of the competition between exchange interactions and the 2D crystalline structure.Our results suggest that the layered Mn_(2)Ga_(2)S_(5)would be an excellent candidate for investigating the physics of 2D magnetism and spin disordered state.