Competing Localized-Itinerant Magnetism Evidenced by Critical Behavior in the Fe_xTi₂S₄ Heideite Sulfides

High Resolution Image Download MS PowerPoint Slide We report the critical behavior of the Fe x Ti 2 S 4 ( x = 0.24, 0.42) intercalated Heideite sulfides in the vicinity of their second-order magnetic phase transition. Several methods including the modified Arrott plot, Widom scaling law, and the critical isotherm analysis reliably yield critical exponents β = 1.105/0.442, γ = 0.913/1.042, and δ = 1.826/3.357, in agreement with the scaling hypothesis, although slightly deviating from the conventional theoretical values. Using the renormalization group theory analysis, we conclude that the exchange distance J ( r ) and the correlation length critical exponent ν indicate that increasing Fe content induces a transition from localized spin interactions, described by the mean-field model, to an itinerant-electron 3D Heisenberg-like model near T C . These features reveal a coupling between short- and long-range magnetic interactions, which are responsible for the unconventional critical behavior in Fe x Ti 2 S 4 . Our results provide valuable insights into the magnetic nature and offer tuning mechanisms in Fe x Ti 2 S 4 intercalated sulfides.