NMR and AFM investigations of nanocavities on the double rare-earth fluoride crystal surface

Abstract

Nanocavities with a size of less than 30 nm on the crystal surface of superfine LiYF 4 powders and single crystals of the Van Vleck paramagnet LiTmF 4 were detected by nuclear magnetic resonance (NMR) cryoporometry and atomic-force microscopy (AFM) and liquid 3 He NMR cryoporometry. NMR investigations show that the nanocavities are evidently present on the surface of the LiYF4 powder particles. The distribution of nanocavities has two maxima corresponding to the specific porous sizes of 3-5 and 10-15 nm. AFM investigations detect the presence of the nanocavities with sizes in the range 50-300 nm on the surface of powder particles and single crystals. The cases of powder microparticles and of a single crystal differ in the value of the parameter "surface roughness", which is 14.5 and 11 nm, respectively. The mechanism of creation of nanocavities is proposed and verified by additional investigations with CaF 2 powders.

Probing Nuclear Dipole Moments and Magnetic Shielding Constants Through 3-Helium NMR Spectroscopy

“…3 He NMR spectroscopy was used for probing the small pores in solid substances e.g. zeolites [58,59], silica aerogels [60] and nanocavities on the crystal surface powders and single crystals [61]. Besides these chemical uses, it is impossible to omit the huge and still growing biological and medicine applications of 3-helium MRI methods.…”