Very large magnetoresistance discovered in single crystals of the ferromagnetic Fe-intercalated transition-metal dichalcogenide ${\mathrm{Fe}}_{0.28}{\mathrm{TaS}}_2$ was attributed to the deviation of the Fe concentration from commensurate values ($x=1/4$ or 1/3), which caused magnetic moment misalignments. Here we report a study of ${\mathrm{Fe}}_x{\mathrm{TaS}}_2$ crystals with $0.23\le x\le 0.35$, demonstrating that crystallographic defects lead to spin disorder, which correlates with magnetotransport properties, such as switching magnetic field $H_S$, magnetoresistance (MR), and even zero-field resistivity ${\rho }_0$ and temperature coefficient $A$ in $\rho \left(T\right)={\rho }_0+A{T}^2$: The ordering temperature $T_C$ and Weiss temperature ${\theta }_W$ are maximized at the superstructure composition $x=1/4$, whereas $H_s$, MR, ${\rho }_0$, and $A$ are minimum. Conversely, at a composition intermediate between the superstructure compositions $x=1/4$ and 1/3, the corresponding magnetotransport properties reach local maxima.

• Received 26 May 2016

DOI:https://doi.org/10.1103/PhysRevB.94.054406