Ferromagnetism and structural transformations caused by Cr intercalation into TiTe₂

Abstract

Crystal structure investigations, electrical resistivity, and magnetic measurements have been performed for polycrystalline samples of intercalated compounds Cr(x)TiTe(2) with a Cr concentration up to x = 0.65. According to the room-temperature x-ray diffraction study of Cr(x)TiTe(2), the initial hexagonal crystal structure transforms to a monoclinic one with increasing Cr content up to x≥0.5 due to the ordering of Cr ions. The intercalation results in the change of the resistivity behavior in Cr(x)TiTe(2) from metal-like at x = 0 to insulator-like above x = 0.33 and leads to ferromagnetic ordering of Cr magnetic moments at x≥0.5. For the compound Cr(0.25)TiTe(2), structural transformations and anomalous resistivity behavior are observed around 230 K, which cannot be explained only by the order-disorder transition within the subsystem of intercalated Cr ions. Structural changes within Te-Ti-Te sandwiches associated with charge density wave instability are suggested to be involved in this phase transition as well.

Transport properties and polarization phenomena in intercalated Ag x HfSe2 compounds

“…Particularly, as it was established for intercalated titanium dichal cogenides, the degree of covalence of the bonds increases as the atomic number of chalcogen increases in a series TiS 2 -TiSe 2 -TiTe 2 [9,11]. The preferen tially covalent character of bonds in M x TiX 2 systems manifests itself in a decrease in unit cell parameter c during intercalation as compared with the initial com pounds [9][10][11]. As opposed to this fact, copper and silver atoms, due to a spherical symmetry of 4s and 5s states, correspondingly, do not possess the tendency to establishment of such bonds, and their intercalation leads to an increase in parameter c as a rule.…”

“…Parent hafnium diselenide was synthesized by the method of solid phase reactions from initial elements in evacuated quartz ampules as it was performed pre viously for the synthesis of titanium dichalcogenides and intercalated materials on their base [9][10][11]. Thus prepared HfSe 2 was used for the subsequent synthesis of intercalated Ag x HfSe 2 samples (x = 0.1, 0.2) by the same procedure.…”

“…The structure and physical properties of interca lated M x TX 2 compounds after the intercalation of M atoms can differ considerably from those characteris tic of the initial compounds [7,9,10]. During the intercalation of 3d atoms of transition metals into the TX 2 structure, intercalated atoms form the bonds with the atoms of adjoining layers of the parent matrix.…”

Selective and low temperature transition metal intercalation in layered tellurides

“…Apparently, the use of less electronegative Te layers (versus O, S, Se and so on) hampers alkali metals intercalation. Interestingly, the related telluride TiTe 2 is known to accommodate Li and Rb, together with transition metals2839404142. Namely, the intercalation selectivity of TiTe 2 and ZrTe 2 can be greatly enhanced by Ti 2 PTe 2 and Zr 2 PTe 2 .…”

“…In this study, we utilize the smaller electronegativity of tellurium to provide a softer Lewis base, compared with O, S and Se27, within the layered tellurides, Ti 2 PTe 2 and Zr 2 PTe 2 , which we expect will promote a higher degree of covalency to selectively bind heavy metals. Prior intercalation studies are largely confined to binary tellurides such as TiTe 2 , ZrTe 2 and IrTe 2 , with a primary interest in superconductivity and ferromagnetism2829. The structure of T 2 PTe 2 ( T =Ti, Zr) is built up of slabs of hexagonal closed-packed triple Te–P–Te layers with T atom being octahedrally coordinated by three Te and three P atoms (see Fig.…”