Efforts are made to determine the absolute specific heat of metals as a function of pressure with an accuracy, which, for the first time, will permit a direct evaluation of the pressure variation of the electronic and phonon parameters gamma and vartheta(D'), respectively. This is achieved by employing the ac method of Sullivan and Seidel, and choosing a suitable sample configuration within a piston-cylinder pressure cell. Essential is the use of diamond powder as a pressure transmitting medium, which because of its low heat capacity and high thermal resistance, couples the sample loosely to the temperature bath, represented by the pressure cylinder. Thus, the thermal requirements of the ac method are met, and corrections--if necessary--are fully tractable. High sensitivity even at the lowest temperatures is obtained by the use of thin slices, prepared from standard carbon resistors, for thermometers. Although delicate, these sensors withstand pressures of more than 20 kbars and remain sensitive. A thorough comparison of results on indium with the literature data at zero pressure is undertaken. It shows that the accuracy of the present results is comparable with that from literature data. Preliminary results at pressures up to 8 kbar are shown; they will be discussed in a separate paper.

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A new ac technique is described which allows the experimental determination of the magnetic field profile near the sample surface in type-II superconductors with pinning. The technique, like a previous method of Campbell. depends only on the validity of the critical-state model and can separate the position and magnetic field dependence of the flux-pinning forces. The entire field profile is obtained from a measurement of the waveform of the response of the sample to a small ac magnetic field superimposed on the dc field. Profiles obtained in cold-worked Nb and Nb-Ti alloys are reported" and the results compared with previous measurements. We have found that the critical-state model does not adequately describe the results obtained on the Nb-Ti alloys when the magnetic field is less than 0.5Hez: 5392

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