Long symmetric high-pressure cell for magnetic measurements in superconducting quantum interference device magnetometer

We describe a high-pressure cell for magnetic measurements in a magnetic property measurement system superconducting quantum interference device (SQUID) magnetometer. The cell has been developed for studies of weakly magnetic materials and has the operating pressure limit of 1 GPa. Its design is focused on reducing the background signal by making the pressure cell symmetric with respect to the sample in order to provide an integrable SQUID response. The use of an externally loaded cylinder has resulted in the increased strength of the cell and in the provision of a larger sample volume. The optimization of the cell's length has made it possible to use the approximation of an infinitely long cylinder in the whole range of accessible pressures and to apply the Lame equation for calculating the change in the diameter of the cell as a function of applied pressure. This enabled us to remove a superconductive manometer from the cell and use the diameter-pressure calibration instead. This has further increased the sensitivity of the measurements at low temperatures which is particularly relevant to studies of weakly magnetic materials. The performance of the cell is illustrated by the results of high-pressure measurements on the molecular antiferromagnet [N(C2H5)(4)][FeCl4]. (c) 2006 American Institute of Physics.