A SYSTEM FOR IN-SITU PRESSURE AND AC SUSCEPTIBILITY MEASUREMENTS USING THE DIAMOND-ANVIL CELL - T(C)(P) FOR HGBA2CUO4+DELTA

Substantial improvements have been made in the sensitivity of an ac su sceptibility measurement system which determines the pressure dependen ce of the superconducting transition temperature, T(c)(P). The pressur e, P, is determined near T(c) from the position of the R1 and R2 fluor escence peaks from ruby chips. The system was used to determine T(c)(P ) for several high T(c) single crystals, but was not sufficiently sens itive to determine T(c)(P) of polycrystalline samples for HgBa2CuO4+de lta. This motivated us to improve the sensitivity of our system. Other parts of the system and the data analysis procedures also have been i mproved. As a demonstration, T(c)(P) of HgBa2CuO4+delta polycrystal to 4 GPa is presented. The improvement of the system using the diamond a nvil cell opens the possibility of measuring T(c) above 10 GPa and on smaller samples.