Single crystals of ${\text{Fe}}_{1/4}{\text{TaS}}_2$ have been studied by using magneto-optical (MO) imaging and radio-frequency magnetic susceptibility, $\chi$. Real-time MO images reveal unusual slow dynamics of dendritic domain formation, the details of which are strongly dependent upon magnetic and thermal history. Measurements of $\chi \left(T\right)$ show well-defined local-moment ferromagnetic transition at $T\approx 155\text{K}$ as well as thermal hysteresis for $50<T<60\text{K}$. This temperature range corresponds to the domain-formation temperature as determined by MO. Together these observations provide strong evidence for local-moment ferromagnetism in ${\text{Fe}}_{1/4}{\text{TaS}}_2$ crystals with large temperature-dependent magnetic anisotropy.

• Received 18 May 2009

DOI:https://doi.org/10.1103/PhysRevB.80.024421