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.

The successful extrusion of short lengths of brittle wires of YBa₂Cu₃O_y that are superconducting above 77 K is reported. Detailed critical current measurements are presented on wires having undergone different physical treatments. The highest critical current obtained from V-I data is ⋍ 90 A/cm², but this particular wire shows clear evidence of flux-pinning forces corresponding to ⋍ 130 A/cm².

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<H_max<7.3 G) and also as a function of temperature (77 K<T<95 K). The remnant magnetization is studied as a function ofH_max 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 ofJ_c is discussed.

We present a calculation of the isothermal magnetization hysteresis curves appropriate to highT_csuperconductors. 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 ofJ_capproaching zero.

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.

We shall discuss magnetization and transport measurements in materials exhibiting a broad first-order transition. The phase transitions would be caused by varying magnetic field as well as temperature, and we concentrate on ferro- to antiferromagnetic transitions in magnetic materials. We distinguish between metastable supercooled phases and metastable glassy phase.

We have measured the transport critical current densityJ_cof sintered YBa₂Cu₃O₇, in various applied fields up to 185 Oe at 77 K. We find a sharp decay ofJ_cwith 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.