Magnetotransport in Fe-intercalated TS2 : Comparison between T=Ti and Ta

Abstract

Sharp magnetization switching and large magnetoresistance (MR) were previously discovered in single crystals of 2H-${\mathrm{Fe}}_{x}{\mathrm{TaS}}_{2}$ and attributed to the Fe superstructure and its defects. We report similar sharp switching and large MR in 1T-${\mathrm{Fe}}_{x}{\mathrm{TiS}}_{2}$ ($0.086\phantom{\rule{0.28em}{0ex}}\ensuremath{\le}\phantom{\rule{0.28em}{0ex}}x\phantom{\rule{0.28em}{0ex}}\ensuremath{\le}0.703$) while providing a side-by-side comparison of the only two such ferromagnetic transition-metal dichalcogenides. The switching field ${H}_{s}$ and MR values are similar in both 1T-${\mathrm{Fe}}_{x}{\mathrm{TiS}}_{2}$ and 2H-${\mathrm{Fe}}_{x}{\mathrm{TaS}}_{2}$, with a larger than expected bowtie $\ensuremath{\rho}(H)$ and a sharper hysteresis loop for $H\ensuremath{\parallel}c$ in the former. The Curie and Weiss temperatures remain roughly constant below $x\phantom{\rule{0.16em}{0ex}}\ensuremath{\sim}\phantom{\rule{0.16em}{0ex}}1/3$ in the $T=\text{Ti}$ single crystals before increasing monotonically for higher $x$, while ${H}_{s}$ and MR reach maxima where defects in the superstructure exist, or a minimum near superstructure compositions, and they remain constant above $x\ensuremath{\sim}0.4$. Despite previous reports, electron diffraction shows only the $\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3}$ superstructure in 1T-${\mathrm{Fe}}_{x}{\mathrm{TiS}}_{2}$. Glassy behavior is shown to coexist within the ferromagnetic state in 1T-${\mathrm{Fe}}_{x}{\mathrm{TiS}}_{2}$ for compositions between 0.1 and 0.703. A simple theoretical model considering first-, second- and third-neighbor interactions yields a phase diagram that accounts for both spin glass behavior and different superstructures.