Na Samarin

Two magnetic transitions and metamagnetism in the R2BaCuO5 (R = Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb) compounds

Specific heat, ac magnetic susceptibility and magnetization in static and in pulse fields were measured for polycrystalline “green phase” R 2 BaCuO 5 (R = Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb) samples. Two magnetic phase transitions were found in these compounds at temperatures T N1 and T N2 . An assumption is made that the antiferromagnetic ordering of copper and rare earth subsystem occurs at T N1 and T N2 , respectively. The Dy, Ho and Er compounds have been shown to be metamagnetic at temperatures below T N2 .

Magnetic interactions in R2BaCuO5 (R=Y, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu) compounds

Abstract Complementary specific heat data on “green phase” R 2 BaCuO 5 (R=Y, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu) compounds and Zn-based Gd 2 BaZnO 5 and Y 2 BaZnO 5 are obtained. Details of phase transition in Dy 2 BaCuO 5 , specific heat upturn in the Yb 2 BaCuO 5 , dimensionality of magnetic interactions in the Y 2 BaCuO 5 and Lu 2 BaCuO 5 , the role of Cu 2+ - O 2− - R 3+ - O 2− - Cu 2+ chains in magnetic exchange are discussed.

Low temperature specific heat of R2Cu2O5 (R = Y, Tb, Dy, Ho, Er, Tm, Yb, Lu) compounds

Specific heat of rare earth cuprates R 2 Cu 2 O 5 (R = Y, Tb-Lu) was measured in the temperature range 2.0 to 30 K. Specific heat anomalies corresponding to antiferromagnetic ordering of Cu 2+ ions have been found. The Neel temperatures vary from T N =10 K (R = Dy) to T N = 25 K (R = Er). For Yb 2 Cu 2 O 5 and Dy 2 Cu 2 O 5 compounds additional sharp peaks are observed at temperatures T = 9.5 K (R = Dy) and T = 6.8 K (R = Yb). These peaks may be associated with a spin-reorientation transition.

Magnetic ordering and metamagnetism in Dy2BaCuO5

Abstract Specific heat, ac magnetic susceptibility and magnetization of the “green phase” Dy 2 BaCuO 5 polycrystalline samples were measured. Two magnetic transitions have been found: antiferromagnetic ordering of Cu 2+ and Dy 3+ magnetic moments at 18 K and 10 K, respectively. The Dy 3+ magnetic ordering is the first order phase transition. The metamagnetic transition in dysprosium subsystem, induced by magnetic field, is observed at temperatures lower than 10 K.

New ternary superconducting germanides

Abstract We have studied the structure, electrical and magnetic properties of new ternary compounds with germanium and transition metals of IV and V groups (Ti 0.7 V 0.3 Ge 3 , Hf 2 V 3 Ge, Zr 32–36 V 32–36 Ge 30–32 , Hf 2 Nb 3 Ge 4 , HfVGe, Zr 15–17 V 39–40 Ge 44–45 , Hf 10.8–21.7 V 36.0–42.8 ). The homogeneity fields for all new phases are determined. Resistivity (T) and magnetic susceptibility χ(T) are investigated at T=4.2…300 K. Two new superconductors have been found — Zr 32–36 V 32–36 Ge 30–32 and HfVGe with T c =4.7 K and 5.7 K, respectively.

Two dimensional variable range hopping in La2-xSrxCuO4-y compounds at low temperatures

Transport (0.03 K T T 2− x Sr x CuO 4− y ceramic samples with x = 0.012, 0.024 and 0.036 are presented. Resistivity of all samples demonstrates two-dimensional variable range hopping law. The corresponding localization radia for all x are calculated.

Superconductivity in AgYBa2Cu3O7−y composites

Abstract The Ag YBa2Cu3O7−y composites with the different Ag-volume fraction x were studied. The critical current density jc of the Ag2O-based material decreases with x. For Ag-based material the maximum of the jc(x)_dependence at x∼20% seems to be caused by a larger sample density. Measurements of the current-voltage characteristics and the effect of magnetic field on the critical current show that the silver addition changes the type of the intergrain links.