Nuclear Resonance Study of Gallium-Substituted Yttrium Iron Garnet

Abstract

Nuclear-magnetic-resonance (NMR) studies have been made of ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$ and of ${}_{}{}^{69}{}_{}{}^{}\mathrm{Ga}$ and ${}_{}{}^{71}{}_{}{}^{}\mathrm{Ga}$ in gallium-substituted yttrium iron garnet (YIG) as a function of gallium substitution at several temperatures. At 4°K the ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$ studies were made up to 43% gallium substitution, while the gallium nmr studies were made up to 55% substitution. Net-magnetization studies have also been made at 77°K up to gallium substitutions of 53%. From the ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$ nmr studies, as well as the net-magnetization studies, we have obtained approximately the site distribution of the iron ions and the magnetizations for the two sublattices. From the experimental concentration dependence of the ${}_{}{}^{71}{}_{}{}^{}\mathrm{Ga}$ hyperfine field we find that in pure YIG in the low-temperature limit the contribution to the Ga hyperfine field at the $d$ site from iron ions on neighboring $d$ sites is 0.57 of the contribution from neighboring $a$ sites and oppositely directed.