Magnetotransport in Fe-intercalated T S2: Comparison between T=Ti and Ta

Sharp magnetization switching and large magnetoresistance (MR) were previously discovered in single crystals of 2H-FexTaS2 and attributed to the Fe superstructure and its defects. We report similar sharp switching and large MR in 1T-FexTiS2 (0.086≤x≤0.703) while providing a side-by-side comparison of the only two such ferromagnetic transition-metal dichalcogenides. The switching field Hs and MR values are similar in both 1T-FexTiS2 and 2H-FexTaS2, with a larger than expected bowtie ρ(H) and a sharper hysteresis loop for Hc in the former. The Curie and Weiss temperatures remain roughly constant below x∼1/3 in the T=Ti single crystals before increasing monotonically for higher x, while Hs and MR reach maxima where defects in the superstructure exist, or a minimum near superstructure compositions, and they remain constant above x∼0.4. Despite previous reports, electron diffraction shows only the 3×3 superstructure in 1T-FexTiS2. Glassy behavior is shown to coexist within the ferromagnetic state in 1T-FexTiS2 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.