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The magnetism in three polycrystalline samples of the electron doped manganites ${\mathrm{Ca}}_{1\ensuremath{-}x}{\mathrm{Pr}}_{x}{\mathrm{MnO}}_{3}$ $(x=0.025,$ 0.05, 0.1) was investigated by NMR on ${}^{55}\mathrm{Mn}$ and ${}^{141}\mathrm{Pr}$ nuclei, neutron diffraction, and magnetic measurements. In all systems the coexistence of majority antiferromagnetic and minority ferromagnetic phases was found. At 4.2 K distinct NMR signals from ferromagnetic domains and antiferromagnetic matrix as well as from the domain walls were detected. Magnetic moment at 4.2 K increases sharply with increasing x from $0.06{\ensuremath{\mu}}_{B}$ pfu $(x=0.025)$ to $0.9{\ensuremath{\mu}}_{B}$ pfu $(x=0.1)$ accompanied by an equally sharp increase of the ferromagnetic NMR signal. For the $x=0.1$ sample the temperature dependence of the ferromagnetic moment determined by neutrons and NMR agrees well with the magnetic measurements. For smaller x the NMR gives essentially the same dependence, while the bulk magnetization decreases with increasing temperature more rapidly, indicating reduction of the ferromagnetic volume when temperature is raised. For a more complete characterization of the system studied the temperature dependencies of the electrical resistivity and thermopower were also measured.

The nuclear quadrupole resonance (NQR) on Ba nuclei was studied in four samples of ${\mathrm{BaBiO}}_{3}$ prepared in different ways and, in addition, in ${\mathrm{BaPbO}}_{3}.$ The spectrum of ${}^{137}\mathrm{Ba}$ at $T=4.2 \mathrm{K}$ consists of a relatively broad line centered near 18 MHz for all ${\mathrm{BaBiO}}_{3}$ samples and near 13 MHz for ${\mathrm{BaPbO}}_{3}.$ The integrated intensity of the ${}^{137}\mathrm{Ba}$ resonance in the ceramic sample of ${\mathrm{BaBiO}}_{3}$ synthesized at $800\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ is approximately twice as large as that in ceramic samples and a single crystal prepared at $930--1080\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}.$ The decrease of the NQR signal can be attributed to the partial disordering of charge-disproportionated Bi ions on the two inequivalent sites. The broadening of the resonance indicates that local distortions of the crystal structure exist in both compounds. The point-charge model was used to analyze the electric-field gradient on the Ba sites.

The NMR of $^{57}\mathrm{Fe}$ in Bi:YIG and La-YIG (where YIG is yttrium iron garnet) polycrystalline samples was measured between liquid-helium and room temperatures. In spectra of both tetrahedral and octahedral ${\mathrm{Fe}}^{3+}$ ions, satellite lines appear, corresponding to ${\mathrm{Fe}}^{3+}$ ions with ${\mathrm{Bi}}^{3+}$ or ${\mathrm{La}}^{3+}$ ions in their vicinity. The resonance frequency ${f}_{\mathrm{res}}$ of the satellites decreases with increasing temperature more slowly than ${f}_{\mathrm{res}}$ of the main lines. The different temperature dependences reflect the enhancement of the ${\mathrm{Fe}}^{3+}$-${\mathrm{Fe}}^{3+}$ superexchange interaction in the vicinity of the diamagnetic substitution. In the simplest model, the presence of ${\mathrm{Bi}}^{3+}$ or ${\mathrm{La}}^{3+}$ leads to two modified exchange integrals. Corresponding changes obtained by the molecular-field analysis are 4.5 and 1.6% for Bi:YIG, while they are 1.3 and 0.5% in the La-doped system. The smaller effect of the ${\mathrm{La}}^{3+}$ ion indicates that local deformation around the substitution plays only a minor role in the enhancement of the superexchange.