Nuclear Magnetic Resonance of Fe⁵⁷ in Various Ferrimagnetic Oxides

Abstract

Enhanced nuclear magnetic resonance of Fe 57 in yttrium iron garnet, nine substituted iron garnets, magnetite and hematite were observed. In garnets two resonances for two positions of Fe 3+ were measured. Resonance frequencies in rare earth substituted iron garnets do not so much differ from the resonance frequencies of Fe 57 in yttrium iron garnet. If one compares relatively accurate resonance frequencies observed in various garnets, it is clearly seen that the effective magnetic field at the nucleus is proportionally increased with their crystal lattice parameters. The fractional variation of this field over all garnets is within four percents on both sites. The resonance of Fe 57 in magnetite is also enhanced by domain wall excitation. Two resonance frequencies corresponding to octahedral and tetrahedral sites were observed at room temperature. Below the transition temperature only one broad resonance was confirmed. A resonance of Fe 57 corresponding for Fe 3+ in hematite was observed on sample containing small amount of magnetite.