Metal-coated carbon nanotube tips for Magnetic Force Microscopy
  We fabricated cantilevers for magnetic force microscopy with carbon nanotube tips coated with magnetic material. Images of a custom hard drive demonstrated 20 nm lateral resolution, with prospects for further improvements. 
Zhifeng Deng, Erhan Yenilmez, Josh Leu, J.E. Hoffman, Eric Straver,   Hongjie Dai, Kathryn A. Moler