Measurements of the magnetic susceptibility, magnetization, electrical resistivity and neutron diffraction have been performed for the compound Fe(0.5)TiS(2) in which Fe atoms are intercalated between S-Ti-S tri-layers. It has been shown that this compound with a monoclinic crystal structure exhibits an antiferromagnetic (AF) ground state below the Néel temperature T(N) ≈ 140 K. Small deviations from the stoichiometry and some disordering effects caused by the additional low-temperature heat treatment do not affect substantially the AF state in Fe(0.5)TiS(2). According to neutron diffraction data the magnetic structure at 2 K is described by the propagation vector k = (1/4,0,1/4). The Fe magnetic moments with a value of (2.9 ± 0.1) μ(B) are directed at an angle of (78.5 ± 1.8)° to the layers. Application of the magnetic field at T < T(N) induces a metamagnetic phase transition to the ferromagnetic (F) state, which is accompanied by the large magnetoresistance effect (|Δρ/ρ| up to 27%). Below 100 K, the field-induced AF-F transition is found to be irreversible, as evidenced by magnetoresistance and neutron diffraction measurements. The magnetization reversal in the metastable F state is accompanied at low temperatures by substantial hysteresis (ΔH ~ 100 kOe) which is associated with the Ising character of Fe ions.

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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.

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Neutron diffraction measurements of the Cr intercalated niobium diselenide Cr 1=3 NbSe 2 together with magnetization measurements have revealed that this compound exhibits ferromagnetic ordering below T C ¼ 96 K unlike a chiral helimagnetic order observed in the sulfide compound Cr 1=3 NbS 2 . As derived from neutron diffraction data, the Cr magnetic moments l Cr ¼ 2.83 6 0.03 l B in Cr 1=3 NbSe 2 are aligned within basal plane. The discrepancy in the magnetic states of Cr 1=3 NbS 2 and Cr 1=3 NbSe 2 is ascribed to the difference in the preferential site occupation of Cr ions in crystal lattices. In Cr 1=3 NbSe 2 , the Cr ions are predominantly distributed over 2b Wyckoff site, which determines a centrosymmetric character of the crystal structure unlike Cr 1=3 NbS 2 , where the Cr ions are mainly located in 2c position and the crystal structure is non-centrosymmetric. V C 2016 AIP Publishing LLC.