We present a comprehensive investigation of the magnetic properties of stage-1 graphite intercalated FeCl$_3$ using a combination of DC and AC magnetic susceptibility, thermoremanent magnetization and field dependent magnetization measurements. This van der Waals system, with a centrosymmetric honeycomb lattice, combines frustration and disorder, due to intercalation, and may be hosting topologically non-trivial magnetic phases. Our study identifies two magnetic phase transitions at $T_{ f1} \approx $ 4.2 K and at $T_{ f2} \approx $ 2.7 K. We find that the paramagnetic state, for $T > T_{ f1}$, is dominated by short-range ferromagnetic correlations. These build up well above $T_{ f1}$ and lead to a significant change in magnetic entropy, which reaches $\Delta S_M^{ Pk} = $ -5.52 J kg$^{ -1}$ K$^{ -1}$ at 7 T. Between $T_{ f1}$ and $T_{ f2}$ we observe slow spin dynamics characteristic of a cluster glass-like state, whereas for $T$ $ < $ $T_{ f2}$ our results indicate the onset of a low temperature long range ordered state. The analysis of the experimental results leads to a complex phase diagram, which may serve as a reference for future investigations searching for topological non-trivial phases in this system.
Categories: cond-mat.dis-nn cond-mat.str-el