Growth and sculpting of Co nano-strings on Si micro-cantilevers: magneto-mechanical properties.

Si micro-cantilevers were coated with Co nano-strings, which were simultaneously grown and sculpted during off-normal pulsed laser deposition. The surface morphology of micro-cantilevers with longitudinal or transverse nano-strings was analysed by scanning tunnelling microscopy. Magnetic anisotropy was detected with a magnetization direction parallel to the nano-strings. The two micro-cantilever types exhibited different mechanical behaviours when placed in a non-uniform magnetic field. By varying the relative position of the micro-cantilever with respect to the gradient direction of this field, a split in the resonant frequency shift of the micro-cantilevers was generated, depending on the direction of magnetic anisotropy. Discrimination was achieved between the micro-cantilevers with transverse nano-strings and the micro-cantilevers with longitudinal nano-strings. The lowest limit of magnetic moment for distinction between these covered micro-cantilevers was 10(-8) emu. The possible benefits of these magneto-mechanical properties for the biological, chemical and physical applications of some nano-mechanical devices are pointed out.