Design Of Opposed-Anvil-Type High-Pressure Cell For Precision Magnetometry And Its Application To Quantum Magnetism

We have developed a highly sensitive technique to conduct magnetometry under high pressures up to 6.3 GPa using an opposed-anvil type cell, which can detect a weak volume susceptibility as small as similar to 10(-4). The high-pressure cell made of non-magnetic binderless tungsten carbide ceramics and CuBe alloy has an optimized geometry to yield a reduced background in the magnetic response, one order of magnitude smaller than those for previously reported high-pressure cells in a commercial SQUID magnetometer. To further increase the sample-signal-to-background ratio, a conical shaped gasket and cupped anvils are introduced to ensure almost ten times better space efficiency. The estimate of background contributions is achieved by taking deformation of the cell parts into account. The magnetization is extracted from the scanned SQUID data using a truncated singular value decomposition (tSVD) linear algebra. tSVD is shown to give more reliable estimate of magnetization than conventional non-linear least-squares (NLLS) analysis. The successful application of the new techniques to the measurements of paramagnetic susceptibilities of spin orbit entangled moment under pressures evidences the drastic improvement of their performance.