The structural and superconducting properties of (Y1-x-yCayHfx)Ba2Cu3Oz samples are investigated ... more The structural and superconducting properties of (Y1-x-yCayHfx)Ba2Cu3Oz samples are investigated using resistivity, ac susceptibility, and dc magnetization measurements. The effect of increasing the Hf concentration in Y1-xHfxBa2Cu3Oz lowers the oxygen content and decreases Tc. The substitution of Ca for Y in (Y0.85-yCayHf0.15)Ba2Cu3Oz provides proper matching between the ionic radius and valence of Y3+ (0.89 Å) and the average ionic radius and valence of Hf4+ (0.78 Å) and Ca2+ (0.99 Å). As the Ca content increases, the Tc increases from y=0 (74 K) to y=0.15-0.20 (compensated oxides) having Tc of 84.5-85.5 K. Magnetization measurements on powdered Hf-doped samples exhibit pronounced M(H) hysteresis loops indicative of extensive flux pinning and enhanced critical currents.
ABSTRACT We provide a recipe to process oxygen-rich Fe-doped YBa2Cu3O7-delta samples, which displ... more ABSTRACT We provide a recipe to process oxygen-rich Fe-doped YBa2Cu3O7-delta samples, which display unusual Fe-dopant site occupancies and superconducting properties. Specifically, we observe substantial occupation of a chain-associated quasi-octahedral site (site E). Room-temperature aging of such samples at ambient conditions leads to the extinction of site E and a concomitant growth of other chain sites, and an increase in Tc. The aged samples display the usual Fe-dopant site distribution and Tc's reported by numerous groups for this superconductor.
The magnetic properties of Ca x Co 1−x Fe 2 O 4 with x varying from 0.0 to 0.4 have been investig... more The magnetic properties of Ca x Co 1−x Fe 2 O 4 with x varying from 0.0 to 0.4 have been investigated by means of Mössbauer spectroscopy and magnetization measurements. Analysis of X-ray diffraction intensity data and Mössbauer data suggests that this system remains in single phase upto ...
ABSTRACT High temperature superconductivity was observed in the system YBa2−xCaxCu3O7−δ for 0 ⩽ x... more ABSTRACT High temperature superconductivity was observed in the system YBa2−xCaxCu3O7−δ for 0 ⩽ x ⩽ 1 by means of resistance and a.c.- usceptibility measurements. It was found that 50% Ca is substituted for Ba in YBa2Cu3O7−gd with transition temperatures at zero resistance vary between 90.0K (x = 0) and 78.0K (x = 1), which may be explained on the basis of deviation from linearity of resistance.
The structural and superconducting properties of (Y1-x-yCayHfx)Ba2Cu3Oz samples are investigated ... more The structural and superconducting properties of (Y1-x-yCayHfx)Ba2Cu3Oz samples are investigated using resistivity, ac susceptibility, and dc magnetization measurements. The effect of increasing the Hf concentration in Y1-xHfxBa2Cu3Oz lowers the oxygen content and decreases Tc. The substitution of Ca for Y in (Y0.85-yCayHf0.15)Ba2Cu3Oz provides proper matching between the ionic radius and valence of Y3+ (0.89 Å) and the average ionic radius and valence of Hf4+ (0.78 Å) and Ca2+ (0.99 Å). As the Ca content increases, the Tc increases from y=0 (74 K) to y=0.15-0.20 (compensated oxides) having Tc of 84.5-85.5 K. Magnetization measurements on powdered Hf-doped samples exhibit pronounced M(H) hysteresis loops indicative of extensive flux pinning and enhanced critical currents.
ABSTRACT We provide a recipe to process oxygen-rich Fe-doped YBa2Cu3O7-delta samples, which displ... more ABSTRACT We provide a recipe to process oxygen-rich Fe-doped YBa2Cu3O7-delta samples, which display unusual Fe-dopant site occupancies and superconducting properties. Specifically, we observe substantial occupation of a chain-associated quasi-octahedral site (site E). Room-temperature aging of such samples at ambient conditions leads to the extinction of site E and a concomitant growth of other chain sites, and an increase in Tc. The aged samples display the usual Fe-dopant site distribution and Tc's reported by numerous groups for this superconductor.
The magnetic properties of Ca x Co 1−x Fe 2 O 4 with x varying from 0.0 to 0.4 have been investig... more The magnetic properties of Ca x Co 1−x Fe 2 O 4 with x varying from 0.0 to 0.4 have been investigated by means of Mössbauer spectroscopy and magnetization measurements. Analysis of X-ray diffraction intensity data and Mössbauer data suggests that this system remains in single phase upto ...
ABSTRACT High temperature superconductivity was observed in the system YBa2−xCaxCu3O7−δ for 0 ⩽ x... more ABSTRACT High temperature superconductivity was observed in the system YBa2−xCaxCu3O7−δ for 0 ⩽ x ⩽ 1 by means of resistance and a.c.- usceptibility measurements. It was found that 50% Ca is substituted for Ba in YBa2Cu3O7−gd with transition temperatures at zero resistance vary between 90.0K (x = 0) and 78.0K (x = 1), which may be explained on the basis of deviation from linearity of resistance.
Uploads
Papers by G. Baldha