P Chaddah

Texture formation and enhanced critical currents in YBa2Cu3O7

We report an increase of a factor up to 5 in JC on mixing varying amounts of Ag2O with YBa2Cu3O7. The increase correlates with an increase in texture as seen by x‐ray diffraction intensities. Microstructure indicates the formation of platelets with c axis normal to the platelets.

Magnetization curves of hard superconductor samples with non-zero demagnetization factor

We present exact solutions of Bean’s critical state model for some sample shapes having non-zero demagnetization factorN. Virgin and hysteresis magnetization curves are obtained for samples in the shape of (i) a sphere (ii) a spheroid (iii) a cylinder of circular cross-section with its axis perpendicular to the field and (iv) a cylinder of elliptical cross section with its axis perpendicular to the field. Some interesting features seen in these first solutions forN ≠ 0 are discussed.

Low field anomaly in magnetization curves

We present a calculation of the isothermal magnetization hysteresis curves appropriate to highTcsuperconductors. We discuss the nature of the low field anomaly as one goes from this strong pinning case to the weak pinning case. We show that the shape of the equilibrium (thermodynamic) magnetization curve is recovered in the limit ofJcapproaching zero.

Do we really need a superconducting glass model

Muller and coworkers have introduced the concept of a superconducting glass to explain some magnetization data in highTcsuperconductors. We explain this data using conventional ideas of type-II superconductivity.

Field and temperature dependence of intergranular hysteresis in YBa2Cu3O7

We have studied the variation of low field magnetization hysteresis in YBa2Cu3O7 as a function of the maximum magnetic field applied during a hysteresis cycle (1 G<Hmax<7.3 G) and also as a function of temperature (77 K<T<95 K). The remnant magnetization is studied as a function ofHmax andT and the measured dependences are explained using the extended critical state model. The potential of this technique as a contactless method of probing the temperature dependence ofJc is discussed.

Critical current measurement on Y-Ba-Cu-O

We report critical current measurements on sintered Y0.35Ba0.65CuOy. The sample, in the perovskite phase, shows zero resistance at 87 K. The critical current transition is seen, in zero field and at 77 K, at a current densityJc of 50 A/cm2.

Effect of correlations on electron momentum density in liquid metals

A scheme to calculate the electron momentum density in simple liquid metals, with the effect ofboth electron correlations and ionic potentials included, is given. This scheme is applied to the case of liquid aluminium. The results are substantially different from calculations considering only the ion potentials, and also from the results for a homogeneous electron gas of corresponding density.

Magnetic field dependence of critical current density in YBa2Cu3O7

We have measured the transport critical current densityJcof sintered YBa2Cu3O7, in various applied fields up to 185 Oe at 77 K. We find a sharp decay ofJcwith magnetic field. We show that this sharp decay is consistent with the low field hysteresis results of Groveret al. We argue that the observed field dependence is not caused by intragranular weak links.

Optimization of superconducting solenoid magnet geometries for minimum inductance

A formalism for obtaining the shape parameters of a solenoid magnet with minimum inductance and excellent field homogeneity is presented. Numerical results are presented for four geometries: viz., the simple solenoid, the split-pair solenoid, the sixth-order inside-notch solenoid and the sixth-order outside-notch solenoid. A comparison is also made with the shape parameters for the minimum volume design of these solenoids.

On the pairing interaction in highT c superconductors

It is argued, from the dependence of the critical current density and ofTc on applied magnetic field, that the pairing interaction in highTc superconductors must be strongly field-dependent.