Nuclear-Magnetic-Resonance Studies ofFe57in Rare-Earth Iron Garnets

Abstract

Nuclear-magnetic-resonance studies of ${\mathrm{Fe}}^{57}$ have been carried out in several rare-earth iron-garnet single crystals (EuIG, TmIG, ErIG, GdIG) and in polycrystalline samples of SmIG and DyIG. The studies were made using the spin-echo technique at 4.2 \ifmmode^\circ\else\textdegree\fi{}K and in some cases at 77 \ifmmode^\circ\else\textdegree\fi{}K. External dc fields of several kG were used in the single-crystal studies to drive out domain walls and were of sufficient magnitude in most cases to align the magnetization along hard as well as easy directions. From studies with the magnetization along 111g and 100g directions, anisotropic effective fields at octahedral and tetrahedral Fe sites could be deduced. The anisotropic effective fields could be largely accounted for by considering the dipolar fields of neighboring magnetic ions. Effects of covalency and transferred hyperfine fields on the isotropic effective fields are also considered.