Miniature capacitive Faraday force magnetometer for magnetization measurements at low temperatures and high magnetic fields

Abstract

A Faraday force magnetometer is presented for measurements of magnetization at temperatures down to 100~mK and in magnetic fields up to 14~T. The specimen is mounted on a flexible cantilever forming a force-sensing capacitor in combination with a fixed back plate. Two different cantilever designs are presented. A torsion resistant cantilever allows to measure magnetization of highly anisotropic single crystal samples. Measurements of the metal organic quantum magnets (C$_5$H$_{12}$N)$_2$CuBr$_4$ (BPCB) and NiCl$_2$$\cdot$4 SC(NH$_2$)$_2$ (DTN) demonstrate the device's capabilities. Routinely, a specimen's magnetic moment is measured with a resolution better than $10^{-7}$ A$\,$m$^2$ ($10^{-4}$ emu). The device in miniaturized to fit is almost any cryostat.