Strategies for solid-state NMR in high-field Bitter and hybrid magnets

Strategies for successful solid-state NMR experiments in high-field Bitter and hybrid magnets are discussed and implemented on an older generation 24 T system. In general, the stability and homogeneity of this type of magnets do not meet the requirements for most NMR experiments. Nevertheless, we will show that a new type of shimming with ferromagnetic inserts, combined with feedback control of the power-supply and NMR reference deconvolution can be used to obtain well-resolved solid-state NMR spectra. We will demonstrate that this approach is especially useful for the study of half-integer quadrupolar nuclei. Experimental results include static and Magic Angle Spinning (MAS) 27Al NMR spectra of the minerals sillimanite and andalusite.