A(NH3)xFePS3 (A = Li, K): intercalated Fe thiophosphate via the liquid ammonia method
Metal phosphorus trichalcogenides (MPX3) are of great interest since these layered materials exhibit wide applications in optical, electrical and magnetic fields. An effective chemical intercalation route for MPX3 which could regulate their physical properties, however, is still lacking. In this work, we show that the liquid ammonia method is an efficient route to co-intercalate alkali metals and NH3 molecules into the gaps in FePS3. After intercalation, the interlayer distance is significantly enlarged by ∼3 Å while the monoclinic lattice (C2/m space group) is still maintained. The structure refinement and EDS measurement suggest that intercalation does not induce any Fe vacancy, thus leading to electron transfer from the alkali metal to [FePS3] layers. Interestingly, magnetic susceptibility shows that the intrinsic anti-ferromagnetic transition in the FePS3 matrix is completely suppressed by this intercalation, whereas a spin-glass state is observed in A(NH3)xFePS3 (A = Li, K) in the lower temperature range (<50 K). The intercalation described in this work is reversible: the alkali metal can be easily de-intercalated using a two-step route and the anti-ferromagnetism reappears accordingly. Meanwhile, the liquid ammonia method is also shown to be efficient at intercalating other MPS3 materials (M = Mn, Co, Ni). Our work not only enriches the intercalation chemistry in the MPX3 system but also provides an excellent route to regulate the magnetic properties of these layered materials.
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