A new superconducting ceramic material CdBa2Cu3O7−δ is obtained. It is found that the superconducting transition (at 86 K) is retained when yttrium is fully replaced by cadmium in the Y-Ba-Cu-O system. X-ray diffraction studies show that the crystalline structure is unchanged and the identified peaks coincide when Y is replaced by Cd in YBa2Cu3O7−δ. Besides a stable superconducting transition, a phase transition near 275 K was seen in the temperature dependence of the specific resistivity which shifted toward lower temperatures (252 K) and then disappeared completely over repeated measurement cycles. The thermal conductivity k of YBa2Cu3O7−δ and CdBa2Cu3O7−δ was found to vary little with temperature up to the superconducting transition. Substituting Cd for Y in the initial HTSC material led to a substantial increase in the lattice thermal conductivity. Measurements of the thermal emf showed that it is positive in YBa2Cu3O7−δ and negative in CdBa2Cu3O7−δ.

The composition of synthesized ceramic samples is investigated by x-ray phase analysis, and it is established that they are high-Tc superconducting Bi2Sr2ZnCu2Ox. It is found that the crystal structure is preserved. To investigate how the superconductivity of Bi–Sr–Ca–Cu–O is influenced by the substitution of calcium by zinc, measurements of the temperature dependence of the resistivity, thermal conductivity, and thermopower (Siebeck coefficient) are carried out. It is found that the substituted compound Bi2Sr2ZnCu2Ox retains its superconducting properties (T0=82K). It is shown that substitution of Ca by Zn leads to an increase of the thermal conductivity. While the thermopower of Bi2Sr2CaCu2Ox shows p-type conductivity in the whole range of temperatures investigated, in Bi2Sr2ZnCu2Ox the type of the conductivity is changed to n-type.

The temperature dependences of the electrical resistivity of CuFeTe 2 semiconductor single crystals with a layered structure are investigated parallel and perpendicular to the plane of the crystal layers in the temperature range 5–300 K. It is demonstrated that, in both cases, the temperature dependences of the electrical resistivity in the temperature range studied are characterized by two portions associated with different mechanisms of electrical conduction. In the high-temperature range, the electrical conduction is predominantly provided by thermally excited impurity charge carriers in the allowed energy band. In the low-temperature range, the electrical conduction occurs through charge carrier hopping between localized states lying in a narrow energy band near the Fermi level. The activation energy for impurity charge carriers is determined. The density of localized states near the Fermi level, the spread in energies of these states, and the average carrier-hopping distances are estimated for different temperatures

We report on magnetic susceptibility, magnetization, electric resistivity, and ESR experiments on single crystals of the covalent-chain antiferromagnetic compounds TlFeX 2 (X = S, Se). Collinear magnetic order with strongly reduced moments sets in at T N =196 K for TlFeS 2 and at T N =290 K for TlFeSe 2 , respectively. The magnetic moments are oriented perpendicular to the chain direction. The temperature dependence of the electric resistivity reveals semiconducting behavior for both compounds. However, high-temperature susceptibility and ESR measurements strongly suggest a one-dimensional metallic character.

From Fe-57 Mossbauer spectroscopy in external fields up to 13.5 T on CoGa2-xFexO4 spinels with x = 1.0, 0.8, 0.3, and 0.2 a preferred substitution of the Co-atoms at the A-sites by Fe with increasing x is concluded. Whereas the internal fields are found to point into nearly the same direction as the applied field for Fe at the A-sites, they point - with deviations of up to 40degrees - into the reverse direction for Fe at the B-sites, indicating an anti ferromagnetic coupling between Fe atoms on the two different. sites. The values of the internal fields increase slightly with x and are higher for iron at the B-sites.

The magnetic properties of system CoGa 2-x Fe x O 4 (x=0.1, 0.2, 0.3, 04, 0.5., 0.8, 1) with spinel structure were investigated by means of dc susceptibility and dc magnetization measurements in magnetic fields 1-12kOe as well as by means of Mossbauer effect. The results of magnetic measurements show that compounds with 0.1 ≤ x ≤ 0.5 exhibit features typical for spin glasses and ones with x=0.8 and 1 have a ferromagnetic ordering. The compounds with x=0.8 and 1 exhibit relaxation behaviour in their Mossbauer spectra.

The Mossbauer investigation of the perovskite-like layer-type ferroelectric-magnetic BiBi4Ti3FeO15 has been carried out in the temperature range form 80°K to 1200°K. The temperature dependence of the quadrupole splitting ΔE(T) gives Tc, = 1010°K which is in good agreement with the dielectric data. The anomalous change of the Mossbauer effect probability in the ferroelectric phase transition region was observed. According to the ΔE(T) curve the ferroelectric phase transition in BiBi4Ti3FeO15 is a second-order transition.

From the temperature dependences of dielectric permittivity the Curie temperatures of ferroelectric-magnetics with the potassium tungsten bronze type structure Sr6Nb9FeO30 and Ba6Nb9FeO30 were determined. It was shown that the magnetic ordering in these crystals may have antiferromagnetic character. The quadrupole splitting of the Mossbauer absorption spectrum of Sr6Nb9FeO30 also exists above the Curie temperature and is probably due to the distribution of the Nb5+ and Fe3+ ions.