Integrated micromechanical cantilever magnetometry of Ga_{1 - x}Mn_xAs

We have developed a technique for fabricating submicron GaAs micromechanical cantilevers into which lithographically patterned samples grown by molecular beam epitaxy or evaporative deposition are integrated. The torque sensitivity of the 100-nm-thick cantilevers makes them ideal for torsional magnetometry of nanometer-scale, anisotropic samples. We present measurements on samples of the ferromagnetic semiconductor Ga_{1 - x}Mn_xAs at temperatures from 350 mK to 65 K and in fields from 0 to 8 T. By measuring the shift in the resonant frequency of the cantilevers, we demonstrate a moment sensitivity of 3 × 10⁶ μ_B at 0.1 T, an improvement of nearly five orders of magnitude upon existing torsional magnetometers.