Millikelvin Torque Magnetometry

Molecular magnetism has relied on the availability of magnetisation data at mK temperatures, since its very beginning. While the micro-SQUID technique has historically been important, other techniques can provide precious information when exported to pushed environments (e.g. mK temperatures and vector fields, and/or fast field-sweep rates). On single crystals, cantilever torque magnetometry (CTM) has been used successfully for these purposes before, but is only rarely available at mK temperatures and with a full 3D rotation of the magnetic field. This can, for example, correct possible misalignments and also, more importantly, allow magnetic torque measurements along any crystal plane.

We have fabricated a very sensitive cantilever torque magnetometer which we use to investigate the anisotropy of molecular magnets, such as rare-earth-containing single-molecule magnets (SMMs) and single-chain magnets (SCMs). The anisotropy is directly manifested through the magnetic torque exerted by the sample on the cantilever, and the torque is detected by measuring the capacitance change between the CuBe cantilever and an underlying metal plate. Using our unique experimental setup we aim at developing a novel tool for a complete vector analysis of the magnetic anisotropy of molecular nanomagnets.