High field-gradient dysprosium tips for magnetic resonance force microscopy

Magnetic resonance force microscopy (MRFM) is based on measuring the attonewton-scale force between nuclear or electronic spins and a magnetic tip. The force is directly proportional to the magnetic field gradient generated by the tip, making a high moment nanoscale magnet desirable. Dysprosium, with a bulk magnetization 70% higher than iron, is a suitable candidate for such a tip. We have performed MRFM to quantitatively characterize two Dy nanomagnets. We find that magnetic field gradients as high as 6MT/m (60G/nm) can be generated, a 40% enhancement compared to our previous FeCo tips. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3673910]