ДИХАЛЬКОГЕНИДЫ НИОБИЯ, ИНТЕРКАЛИРОВАННЫЕ ХРОМ
Аннотация
The presented final qualifying work of the master is devoted to the study of the influence of chromium intercalation on the structure and physical properties of niobium dichalcogenides.
In the present work, the compounds CrxNbSe2 (0 ≤ x ≤ 0.5) and CrxNbTe2 (0 ≤ x ≤ 0.75) were studied in detail using X-ray diffraction, magnetization and electrical resistivity measurements. Synthesis of polycrystalline samples was carried out by a two-stage solid-state reaction method. The crystallographic parameters were determined using a Bruker D8 Advance X-ray diffractometer. The measurements of the magnetization and magnetic susceptibility were performed by means of a SQUID MPMS (Quantum Design) magnetometer in the temperature interval from 2 up to 300 K in magnetic fields up to 70 kOe. The electrical resistivity was measured by a four-probe dc method in the temperature range 5 K – 300 K with using a closed-cycle refrigerator.
X-ray certification and analysis of the obtained diffractograms showed that almost all compounds are single-phase. Data on the crystal structure of the samples and their structural changes are obtained. Studies of the kinetic properties have shown that the samples of the CrxNbSe2 system to a concentration of x = 0.5 have a metallic conductivity type and the samples of the CrxNbTe2 system with a chromium concentration of x = 0.25 and x = 0.5 in the temperature range above 50 K have a metallic conductivity type as well as the compounds - matrixes. Abnormal behavior was found in chromium-containing compounds at low temperatures. The analysis of temperature and field dependences of magnetization for all obtained compounds was carried out. As a result, it was shown that compounds with high chromium content exhibit ferromagnetic ordering at low temperatures. In addition, a comparative analysis of the characteristics of compounds with a fixed percentage of chromium in the sample and different chalcogen in the structure of the compound matrix was carried out.
In the present work, the compounds CrxNbSe2 (0 ≤ x ≤ 0.5) and CrxNbTe2 (0 ≤ x ≤ 0.75) were studied in detail using X-ray diffraction, magnetization and electrical resistivity measurements. Synthesis of polycrystalline samples was carried out by a two-stage solid-state reaction method. The crystallographic parameters were determined using a Bruker D8 Advance X-ray diffractometer. The measurements of the magnetization and magnetic susceptibility were performed by means of a SQUID MPMS (Quantum Design) magnetometer in the temperature interval from 2 up to 300 K in magnetic fields up to 70 kOe. The electrical resistivity was measured by a four-probe dc method in the temperature range 5 K – 300 K with using a closed-cycle refrigerator.
X-ray certification and analysis of the obtained diffractograms showed that almost all compounds are single-phase. Data on the crystal structure of the samples and their structural changes are obtained. Studies of the kinetic properties have shown that the samples of the CrxNbSe2 system to a concentration of x = 0.5 have a metallic conductivity type and the samples of the CrxNbTe2 system with a chromium concentration of x = 0.25 and x = 0.5 in the temperature range above 50 K have a metallic conductivity type as well as the compounds - matrixes. Abnormal behavior was found in chromium-containing compounds at low temperatures. The analysis of temperature and field dependences of magnetization for all obtained compounds was carried out. As a result, it was shown that compounds with high chromium content exhibit ferromagnetic ordering at low temperatures. In addition, a comparative analysis of the characteristics of compounds with a fixed percentage of chromium in the sample and different chalcogen in the structure of the compound matrix was carried out.