Direct observation of local magnetic field generated by micromagnet

Using standard nuclear magnetic resonance (NMR) technique and a well-fabricated sample, we have succeeded in directly observing local magnetic field generated by a micromagnet Ni₄₅ Fe₅₅ (with thickness of 400 nm), which was sputtered on an Al layer of 20 nm thickness. Improved sensitivity of our NMR technique enabled us to clearly observe Al-NMR signals, which are confirmed to come from Al nuclei in the 20 nm layers. From the analysis of the Al-NMR spectra, the local magnetic field was found to be +0.17±0.02 (-0.20±0.01) T, the sign of which is consistent with the geometry that the external magnetic field was applied perpendicular (parallel) to the Al layer. The present study gives a potential key element toward realizing higher resolution in magnetic resonance imaging.