Sharp switching of the magnetization in Fe$_{1/4}$TaS$_{2}$

Anisotropic magnetotransport measurements are reported on ${\mathrm{Fe}}_{1∕4}\mathrm{Ta}{\mathrm{S}}_{2}$ single crystals grown by vapor transport. Both the magnetization and resistivity are extremely anisotropic, with the magnetic moments aligned parallel to the $c$ crystallographic direction. ${\mathrm{Fe}}_{1∕4}\mathrm{Ta}{\mathrm{S}}_{2}$ orders ferromagnetically below ${T}_{C}=160\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ and displays very sharp hysteresis loops in the ordered state for $H\ensuremath{\Vert}c$. The corresponding magnetoresistance is negative, and it qualitatively reproduces the features observed in the $M(H)$ data by showing a sharp drop around the critical field ${H}_{s}$ for the moment reversal. The magnetization switching time shows an unusual increase with increasing temperature. For field applied within the $ab$ plane, the magnetization remains small and linear in field up to $5\phantom{\rule{0.3em}{0ex}}\mathrm{T}$, and the magnetoresistance is positive and quadratic in field, with no visible hysteresis. The squareness of the $H\ensuremath{\Vert}c$ $M(H)$ loops and the high critical field for the magnetization switch (${H}_{s}=3.7\phantom{\rule{0.3em}{0ex}}\mathrm{T}$ at $T=2\phantom{\rule{0.3em}{0ex}}\mathrm{K}$) allow us to classify ${\mathrm{Fe}}_{1∕4}\mathrm{Ta}{\mathrm{S}}_{2}$ as a strong ferromagnet.