FORCE-DETECTED MAGNETIC-RESONANCE IN A FIELD GRADIENT OF 250000 TESLAPER METER

We report the detection of slice-selective electron spin resonance wit h an external magnetic field gradient comparable to local interatomic gradients, using the techniques of magnetic resonance force microscopy . An applied microwave field modulated the spin-gradient force between a paramagnetic DPPH sample and a micrometer-scale ferromagnetic tip o n a force microscope cantilever. A sensitivity equivalent to 184 polar ized electron moments in a one-Hertz detection bandwidth was attained. We mapped the tip magnetic field with a resonant slice thickness of o rder one nanometer, thereby demonstrating magnetic resonance on length scales comparable to molecular dimensions. (C) 1998 American Institut e of Physics. [S0003-6951(98)03647-X].