Magnetic susceptibility measurements at high pressure using designer diamond anvils

High pressure magnetic susceptibility experiments can yield valuable insights into the changes in magnetic behavior and electron correlation properties which can accompany extreme compressions of matter. However, magnetic susceptibility experiments with ultrahigh pressure diamond anvil cells are extremely challenging due to the very small size of the high-pressure sample (approximate to75 mum diameter) and the difficulty of obtaining good coupling between the sample and the sensing coil. As a result, measurement sensitivity and poor signal-to-background ratios tend to be serious concerns which limit the applicability of these experiments. We present here a new approach to high-pressure ac magnetic susceptibility experiments that involve specially fabricated diamond anvils with diamond encapsulated sensing microcoils which are located just 10-20 mum from the high-pressure sample. We also present some test results taken with a gadolinium sample in order to demonstrate the viability of this high-pressure ac susceptibility technique. (C) 2003 American Institute of Physics.