V. G. Pleshchev

The effect of intercalation by 3d elements on the structure and physical properties of titanium diselenide MxTiSe2 (M=Cr, Fe, Co)

The dependences of the structural parameters and the electrical and magnetic properties of titanium diselenide, intercalated by chromium, iron, and cobalt on the intercalant concentration and temperature were studied experimentally. The possibility of the involvement of d electrons in the formation of interlayer covalent bonds in relation to the 3d-shell filling of intercalated ion is discussed.

Hierarchy of percolation thresholds and the mechanism for reduction of magnetic moments of transition metals intercalated into TiSe2

The concentration dependences of the effective magnetic moment of transition metal atoms intercalated into TiSe2 are analyzed in the framework of the percolation theory. It is shown that, depending on the degree of localization of impurity states, the effective magnetic moment is determined by the overlap of 3d orbitals of transition metals or orbitals of titanium atoms coordinated by impurity atoms.

Magnetic state and properties of the Fe0.5TiSe2 intercalation compound

The Fe0.5TiSe2 compound with a monoclinic crystal structure has been prepared by intercalation of Fe atoms between Se-Ti-Se sandwiches in the layered structure of TiSe2. The crystal and magnetic structures, electrical resistivity, and magnetization of the Fe0.5TiSe2 compound have been investigated. According to the neutron diffraction data, the Fe0.5TiSe2 compound has a tilted antiferromagnetic structure at temperatures below the Néel temperature of 135 K, in which the magnetic moments of Fe atoms are antiferromagnetically ordered inside layers and located at an angle of approximately 74.4° with respect to the layer plane. The magnetic moment of Fe atoms is equal to (2.98 ± 0.05)μB. The antiferromagnetic ordering is accompanied by anisotropic spontaneous magnetostrictive distortions of the crystal lattice, which is associated with the spin-orbit interaction and the effect of the crystal field.

Electrical and magnetic properties of titanium diselenide intercalated with cobalt

This paper discusses experimental studies of the temperature dependence of the magnetic susceptibility, electrical conductivity, and Seebeck coefficient of the compounds CoxTiSe2 (0.1⩽x⩽0.5), along with the structural behavior exhibited by these compounds. For Co0.5TiSe2, the observed temperature dependence of the magnetic susceptibility is characteristic of an antiferromagnet with a Néel temperature of 510 K. The data obtained on the structural characteristics and physical properties of the intercalated phases are interpreted using a model that assumes the formation of bands of localized states near the Fermi level.

Structural and Physical Properties of Cobalt-Intercalated Titanium Diselenide and Ditelluride Compounds

A complex investigation of the structural, electrical, and magnetic properties of cobalt-intercalated titanium diselenide and ditelluride compounds at different intercalant concentrations and temperatures is performed for the first time. The influence of the matrix on the physical characteristics of the intercalation materials is analyzed.

Magnetic and electrical properties of intercalated phases in the (Cr, Cu)-HfSe2 system

It has been shown that intercalation of the HfSe2 compound with chromium atoms results in an increase in the magnetic susceptibility and a decrease in the resistivity while retaining the semiconductor conductivity type. The CrxHfSe2 compounds exhibit a paramagnetic behavior at temperatures above 2 K in the entire concentration range 0 ≤ x ≤ 0.25. It has been revealed that an increase in the electron density due to additional introduction of copper can cause the appearance of a cluster-spin-glass-type state in CrxCuyHfSe2 compounds. The data obtained indicate a large role of the indirect exchange interaction via conduction electrons in the formation of the magnetic state in layered intercalated compounds based on transition metal dichalcogenides.

Specific features of the structure, magnetic properties, and heat capacity of intercalated compounds CrxTiSe2

Structural features, magnetic properties, and heat capacity of CrxTiSe2 intercalated compounds with a layered structure have been studied experimentally for 0 ≤ x ≤ 0.5. It is shown that, at high chromium concentrations (x > 0.25), the magnetic properties of the compounds are strongly affected by the degree of ordering and distribution pattern of the intercalated atoms. Depending on the cooling rate of samples of the same composition (x = 0.5), an antiferromagnetic or a cluster-glass-type state can be obtained. Heat capacity measurements have revealed a nonmonotonic variation in the lattice rigidity with increasing concentration of intercalated atoms.

Influence of the chalcogen substitution on the character of magnetic ordering in Fe0.5TiS2 − xSex intercalated compounds

The crystal structure and magnetic properties of layered Fe0.5TiS2 − xSex (0 ≤ x ≤ 2) compounds intercalated by iron atoms have been investigated. It has been shown that the substitution of selenium for sulfur is accompanied by an increase in the unit cell volume, a transition from the ferromagnetic to antiferromagnetic behavior, and a nonmonotonic variation in the paramagnetic Curie temperature. The intercalated iron atoms are characterized by lower values of the effective moment (3.4–4.0μB) as compared to the predicted value (4.89μB) for the Fe2+ ion at g = 2. The results obtained have been discussed under the assumption that there are the hybridization of 3d electronic states of intercalated Fe atoms with the electronic states of the TiS2 − xSex host compounds and the competition of exchange interactions of different types.

Structural phase transformations and physical properties of intercalation compounds in the Cr0.5Ti(Se1−x Tex)2 system

The atomic structure and magnetic and electric properties of the Cr0.5TiSe2-Cr0.5TiTe2 system of intercalated phases were studied in detail by gradually replacing selenium by tellurium. It was revealed that this replacement changes the crystalline structure from monoclinic in the initial compounds to hexagonal in the compounds containing various types of chalcogen atoms; this is accompanied by disordering of chromium atoms in the van der Waals gaps. The electrical resistance and magnetic characteristics vary nonmonotonically on replacement of selenium by tellurium, which is associated with a change in the degree of atomic disordering during the transition from Cr0.5TiSe2 to Cr0.5TiTe2.

Magnetic state of intercalation compounds in the CrxTiTe2 system

The temperature and field dependences of the magnetic characteristics of chromium-intercalated titanium ditelluride compounds are investigated over a wide range of chromium concentrations. The Cr0.5TiTe2 compound is studied by neutron diffraction. It is revealed that the system under investigation can occur in different magnetic states depending on the chromium concentration. An analysis of the experimental results demonstrates that the interaction between magnetic moments of chromium ions is predominantly ferromagnetic in character. An increase in the chromium concentration leads to ferromagnetic behavior with a pronounced magnetic hysteresis. The magnetic moments of chromium ions in these compounds are estimated.