New Fe-based layered telluride Fe_3−δAs_1−yTe₂: synthesis, crystal structure and physical properties

Abstract

A new ternary telluride, FeAsTe, was synthesized from elements at 600 °C. It crystallizes in the hexagonal P6/mmc space group with the unit cell parameters a = 3.85091(9) Å and c = 17.1367(4) Å for δ = 0.3 and y = 0.04. Its layered crystal structure contains partially occupied intralayer and interlayer Fe positions, which give rise to significant nonstoichiometry: FeAsTe was found to possess the homogeneity range of 0.25 < δ < 0.45 and y = 0.04. Regions of local vacancy ordering alternate with regions of randomly distributed vacancies, so that the ordering of Fe atoms and vacancies is not complete in the average structure. Clear evidence of the magnetic phase transition is obtained by thermodynamic measurements, Mössbauer spectroscopy, and neutron powder diffraction. Magnetic susceptibility measurements reveal weak ferromagnetism below T = 123 K with a net moment of M∼ 0.1μ/Fe at T = 2 K. This transition is confirmed by differential scanning calorimetry. Additionally, neutron powder diffraction indicates the onset of a complex AFM-like magnetic ordering below 100 K.

Nearly room temperature ferromagnetism in a magnetic metal-rich van der Waals metal

“…The collection semiangles of the HAADF detector were adjusted from 68 to 280 mrad to collect scattered electrons in a large angle for clear Z-sensitive images. The annular bright field images (17,20,32), Fe-based metallic vdW ferromagnets (solid symbols) (23,(25)(26)(27)(40)(41)(42), and the ferromagnetic TMDC compounds (crosses) with intercalation of magnetic transition metal atoms (M = Fe, Cr, and Mn) (43)(44)(45)(46). Among them, Fe n GeTe 2 compounds exhibit high T c and high M sat .…”

“…The temperature and the magnetization per Fe atom are normalized by those of Fe 3 GeTe 2 to show their relative changes. (B) Ferromagnetic transition temperature T c and saturation magnetization M sat for various vdW-type ferromagnets, including Cr-based insulating vdW ferromagnets (open symbols)(17,20,32), Fe-based metallic vdW ferromagnets (solid symbols)(23,(25)(26)(27)(40)(41)(42), and the ferromagnetic TMDC compounds (crosses) with intercalation of magnetic transition metal atoms (M = Fe, Cr, and Mn)(43)(44)(45)(46). Among them, Fe n GeTe 2 compounds exhibit high T c and high M sat .…”

The van der Waals Ferromagnets Fe5–δGeTe2 and Fe5–δ–xNixGeTe2 – Crystal Structure, Stacking Faults, and Magnetic Properties

“…Thus, suppression of the magnetic ordering was achieved in the solid solution Fe 3– δ Ge 1– x As x Te 2 and attributed to the elongation of the Fe–Fe distances of the pure Fe layers . Since the other isotypic compounds Ni 3 E Te 2 ( E = Ga, In, Sn) and Ni 2 SbTe 2 exist, beside Ni 3 GeTe 2 and Fe 3 AsTe 2 , there is room for further investigations in this field , . Fe 2.3 GeTe is a further compound in the Fe–Ge–Te system showing comparable structure motifs to Fe 3 GeTe 2 and is ferromagnetic below 239 K .…”

Tuning the Room Temperature Ferromagnetism in Fe5GeTe2 by Arsenic Substitution

“…Interestingly, ρ also increases upon cooling in Fe 3−x AsTe 2 whereas Fe 3−x GeTe 2 has bad metal like behavior. [31,36] As shown in Fig. 5a, the resistivity in Fe 4.8 AsTe 2 has a small anomaly near the magnetic transition and it increases more rapidly upon cooling below T N .…”