Three dimensional magnetic resonance imaging by magnetic resonance force microscopy with a sharp magnetic needle

An electropolished magnetic needle made of Nd₂Fe₁₄B permanent magnet was used for obtaining better spatial resolution than that achieved in our previous work. We observed the magnetic field gradient |G _Z| = 80.0 G/μm and the field strength B = 1250 G at Z ∼ 8.8 μm from the top of the needle. The use of this needle for three dimensional magnetic resonance force microscopy at room temperature allowed us to achieve the voxel resolution to be 0.6 μm × 0.6 μm × 0.7 μm in the reconstructed image of DPPH phantom. The acquisition time spent for the whole data collection over 64 × 64 × 16 points, including an iterative signal average by six times per point, was about 10 days.