Coexistence of antiferromagnetism and ferromagnetism inCa1−xPrxMnO3 (x<~0.1)manganites

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.