Piezoresistive torque magnetometry below 1 K

We have investigated the performance of piezoresistive cantilevers as magnetometers in the temperature range below 1 K. The de Haas-van Alphen effect was used to study the temperature dependence of a sample of kappa-(BEDT-TTF)(2)Cu(NCS)(2), fixed on the end of a cantilever, as a function of the excitation current through the piezoresistive device. We found that by using a small thermalizing wire connected directly to the sample, large excitations were not incompatible with sample temperatures remaining low, thereby establishing the use of these devices as sensitive magnetometers well below 1 K. A large hysteretic behavior observed at low fields (below 0.01 T) and low temperature (below similar to 2 K) precludes their use in that regime. (C) 1999 American Institute of Physics. [S0003-6951(99)01503-X].