Magnetic Phase Transitions in Nanostructured Mn-intercalated TaS$_{2}$

Samples of nanostructured Mn-intercalated TaS$_{2}$ with different concentrations of Mn have been fabricated. Previous work on nanostructured Mn$_{x}$TaS$_{2}$ has shown that ferromagnetism competes with a cluster-glass phase as the atomic fraction $x$ of Mn increases. There is a tricritical point near $x=$ 0.23 as indicated by critical exponent values significantly greater than those associated with the three-dimensional Ising or Heisenberg models. To further understand the phase diagram, we have studied nanostructured Mn$_{x}$TaS$_{2}$ with $x=$ 0.235. dc magnetization and ac susceptibility measurements indicate that there are two transitions as the temperature is varied. Arrott-Noakes and Kouvel-Fisher analyses indicate a ferromagnetic transition at $T_{C}=$ 74 K, with critical exponent values $\beta =0.86$ and $\gamma =1.22$. The anomalous $\beta $ value associated with the ferromagnetic transition was also seen in the sample that exhibited tricritical-like behavior. There is a sharp increase in the susceptibility as the temperature is lowered, with a peak occurring near 40 K. An excellent Vogel-Fulcher fit to the dynamic susceptibility data confirms a cluster glass transition. Our current results are consistent with a steep boundary between the ferromagnetic and cluster-glass phases.