Nuclear-Magnetic-Resonance Studies ofFe57in Barium Ferrite

The nuclear magnetic resonance of ${\mathrm{Fe}}^{57}$ has been studied in single-crystal and polycrystalline samples of barium ferrite (Be${\mathrm{Fe}}_{12}$ ${\mathrm{O}}_{19}$). The resonance spectrum has been obtained by plotting the amplitude of the ${\mathrm{Fe}}^{57}$ spin-echo signals as a function of frequency. The zero-field spectrum has been studied at both 4.2 and 77°K. The spectrum at 4.2°K has also been studied with externally applied static fields of up to 8.8 kG, using oriented single-domain powders. Five hyperfind fields are resolved, corresponding to the five magnetically and crystallographically inequivalent lattice sites of Ba${\mathrm{Fe}}_{12}$ ${\mathrm{O}}_{19}$. Studies of the temperature dependence of the hyperfine fields are made up to 180°K, and the hyperfine fields are compared with those obtained from Mössbauer studies. Values of the hyperfine fields associated with the various crystallographic lattice sites are discussed.