The dominating component of most NMR instruments is the magnet, as it typically exceeds the electronics and the sample in size and weight. To shrink the complete instrument to compact size, a prime challenge rests in the miniaturization of the magnet. In this endeavor, most efforts today focus on magnets from permanently magnetic materials. This chapter summarizes the state of the art of compact, permanent NMR magnets and explores new design concepts that may guide the construction of small permanent magnets with high magnetic fields or fields sufficiently homogeneous to resolve the chemical shift in NMR spectra of liquids.
Blümich, C. Rehorn, W. Zia, Magnets for Small‐Scale and Portable NMR, in: J. Anders, J.G. Korvink, eds., Micro and Nano Scale NMR: Technologies and Systems, Wiley VCH, Weinheim, 2018, pp. 1-20. https://application.wiley-vch.de/books/sample/3527340564_c01.pdf