Nuclear-Magnetic-Resonance Studies ofEu151andEu153in Europium Iron Garnet Single Crystals

Abstract

The nuclear magnetic resonances of ${\mathrm{Eu}}^{151}$ and ${\mathrm{Eu}}^{153}$ have been studied at 4.2\ifmmode^\circ\else\textdegree\fi{}K in single crystals of europium iron garnet with externally applied fields of sufficient magnitude to align the magnetization along various crystallographic directions. Hyperfine field and quadrupole splitting parameters of the ${\mathrm{Eu}}^{+3}$ ions are obtained. Hyperfine fields along the principal orthorhombic axes ($x$, $y$, and $z$) of the rare-earth sites are found to be 649, 706, and 382 kG, respectively, where the $z$ axis corresponds to the orthorhombic axis which lies along the cubic [100] direction. The anisotropy of the hyperfine field is shown to be due in part to the crystal field distortion and in part to the anisotropy of the exchange fields arising from the iron ions. From the ${\mathrm{Eu}}^{153}$ quadrupole splittings, contributions to the electric field gradient arising from the crystal fields and the exchange fields are obtained. Values of the crystal field parameters and anisotropic exchange fields are obtained and discussed in relation to those in other rare-earth iron garnets.