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-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 H c in the former. The Curie and Weiss temperatures remain roughly constant below x ∼ 1/3 in the T = Ti single crystals, before monotonically increasing for higher x, while Hs and MR reach maxima where defects in the superstructure exist, or a minimum near superstructures compositions, and 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 which accounts for both spin glass behavior and for different superstructures.

Clarification of the ordering of intercalated Fe atoms in Fe x TiS2 and its effect on the magnetic properties

“…However, this might not be the case since the Fe atoms might have local Fe ordering, which could not be detected because of the limitations of XRD measurement. Choe et al (2019) managed to identify local Fe ordering of ffiffi ffi 3 p a  ffiffi ffi 3 p a in Fe x TiS 2 over a wide range of Fe concentration (0.086 x 0.70) using transmission electron diffraction (TED) and these Fe x TiS 2 crystals exhibited the coexistence of glassy and ferromagnetic magnetic states, which differed from previous reports. So, TED seems to be a useful alternative in identifying the local ordering of intercalated Fe atoms in Fe x TiS 2 .…”

“…Layered structures like transition metal dichalcogenides (TMDC) attract much attention because of the possibility of intercalating different atoms or molecules between the layers to create new functionalities such as magnetism (Negishi, Shoube et al, 1987;Negishi, Ohara et al, 1988;Inoue et al, 1989;Koyano et al, 1994;Baranov et al, 2005Baranov et al, , 2009Baranov et al, , 2010Shand et al, 2012;Choe et al, 2019), superconductivity (Somoano & Rembaum, 1971;O nuki et al, 1982;Ahmad et al, 1987;Wang et al, 2018), thermoelectricity (Guilmeau et al, 2017(Guilmeau et al, , 2011Pawula et al, 2019) and the appearance of chargedensity-wave states (Baranov et al, 2007). These intercalated TMDCs display different properties as compared to the host structure because of the 'host-guest' interactions (Rao & Shafer, 1979;Inoue et al, 1989) and 'guest-guest' interactions (Inoue et al, 1994;Negishi et al, 2000a,b;Roth et al, 2016) as new molecular orbitals are formed by hybridization (Rao & Shafer, 1979;Negishi, Shoube et al, 1987;Yamasaki et al, 1987;Suzuki et al, 1993;Dresselhaus, 2013).…”

“…ISSN 2052-5206 Titanium disulfide (TiS 2 ), one of the TMDC materials, has been reported to show different magnetic properties depending on the nature and concentration of intercalated magnetic atoms such as V, Cr, Mn, Fe and Co. For example, V x TiS 2 and Mn x TiS 2 at x 0.1 displayed the paramagnetic phase, whereas Cr x TiS 2 displayed the ferromagnetic phase at x 0.75 and the ferromagnetic one at x = 1 (Negishi, Shoube et al, 1987;Inoue et al, 1989). In the case of Fe x TiS 2 , which has the advantages of sharp switching and large magnetoresistance (Choe et al, 2019;Selezneva et al, 2021), several magnetic phases were reported: spin-glass phase at x < 0.20, cluster-glass phase at 0.20 x 0.40 and ferromagnetic phase at x > 0.40 (Yoshioka & Tazuke, 1985;Negishi, Shoube et al, 1987;. However, subsequent studies showed contradictory results, with the findings of coexistence of glassy and ferromagnetic phases for 0.086 x 0.70 (Choe et al, 2019), as well as the antiferromagnetic phase at x = 0.50 (Baranov et al, 2013).…”

“…In the case of Fe x TiS 2 , which has the advantages of sharp switching and large magnetoresistance (Choe et al, 2019;Selezneva et al, 2021), several magnetic phases were reported: spin-glass phase at x < 0.20, cluster-glass phase at 0.20 x 0.40 and ferromagnetic phase at x > 0.40 (Yoshioka & Tazuke, 1985;Negishi, Shoube et al, 1987;. However, subsequent studies showed contradictory results, with the findings of coexistence of glassy and ferromagnetic phases for 0.086 x 0.70 (Choe et al, 2019), as well as the antiferromagnetic phase at x = 0.50 (Baranov et al, 2013). One possible reason for the discrepancy in the magnetic states is the different types of Fe x TiS 2 structures identified, i.e.…”

Intercalated phases of transition metal dichalcogenides

“…145 Fe-intercalated 2H-TaS 2 and 1T-TiS 2 possess out-of-plane FM order, in which an MR of 150% is achievable at certain Fe concentrations ( Figure 10B,C). 146 The out-of-plane easy axis is attributed to the large, unquenched, out-of-plane orbital magnetic moments of Fe atoms, 147,148 and the large MR arises from spin-disorder scattering in the strong spin-orbit coupling environment. 149 By contrast, other TMDs intercalated with Fe element show AFM order.…”