A simple uniaxial pressure device for electrical resistivity measurements: Suitable for closed cycle refrigerator system

Abstract

A simple uniaxial pressure device suitable for closed cycle refrigerator system (CCRS) has been built. This device in principle is applicable to any crystal. In this device the pressure can be varied smoothly and continuously to any desired temperature using a disc-micrometer and a spring – holder attachment, which are kept on the demountable top flange of the vacuum shroud of CCRS at room temperature. This device is not dependent on pressure calibration and the pressure calculation is obtained directly from the surface area of the crystal, the rotations of the disc-micrometer and the spring – constant value of the spring. Piezoresistance measurements were made on n-type Si to check the quality of data from the uniaxial pressure device. The performance of the uniaxial pressure device is illustrated by investigating the uniaxial pressure dependence of bilayer manganite La1.25Sr1.75Mn2O7 single crystals along the ab-plane and c-axis using electrical resistivity measurements down to 15 K. We found that the peak resistivity measured with the current parallel to the ab-plane and the pressure parallel to the c-axis reduced ∼50% of its resistivity at 120 MPa. The resistivity increased to ∼460% at 120 MPa with the current parallel to the c-axis and the pressure parallel to the ab-plane. The metal-insulator transition drastically enhances (dTMI∕dPc=+46.33K∕GPa) when the pressure is parallel to the c-axis and decreases moderately (dTMI∕dPab=−16.58K∕GPa) when the pressure is parallel to the ab-plane. The change of ρab with the pressure parallel to the c-axis is almost equivalent to change of ρab under external magnetic field of ∼8Tesla.