Measurements of electrical resistance of HTSC single crystals under hydrostatic pressures up to 1.5 GPa

An apparatus is described for the high-precision measurement of electrical resistance of HTSC samples under pressures of up to 1.5 GPa in compressed helium as a function of temperature within a range from 30 to 400 K. Measurements are performed with the four-probe technique simultaneously on two samples, which makes it possible to investigate the anisotropy of the resistivity of HTSC single crystals. A method is proposed to introduce a thermocouple into a pressure vessel so that it is not necessary to take into account corrections for the thermal emf of the thermocouple as a function of pressure. The reproducibility of the results of measuring temperatures of samples is similar to 0.02 K, and the pressure is determined to an accuracy of 1 MPa.