No abstract

Polycrystalline Lu-doped YFeO3 samples with perovskite structure were synthesized by solid-state reaction. Powder X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray analysis manifest the high quality of the samples. Room temperature 57Fe Mössbauer spectra indicate that only the Fe3+ exists in the samples, which excludes the formation of multiple valence of Fe. The large effective magnetic moments of Fe3+ obtained from the temperature dependence of magnetization data can be explained in terms of the formation of ferromagnetic clusters. Field-dependent magnetization reveals that all the samples show weak ferromagnetic property due to the small canting of the Fe3+ moments. The field-induced spin-reorientation was detected on YFeO3 and was gradually suppressed by Lu3+ doping. Polarization hysteresis loops of Y1−xLuxFeO3 (0 ≤ x ≤ 1) were observed at room temperature. Our results suggest that the multiferroic properties may exist in the Y1−xLuxFeO3 (0 ≤ x ≤ 1) ceramics.

No abstract

Magnetic properties and magnetoresistance effect of Pb2FeMoO6, synthesized under high pressure at high temperature, were systematically studied. The sample shows ferromagnetic behavior with Curie temperature about 243 K. The field dependent of paramagnetic susceptibility was discussed by the magnetic inhomogeneous related to Fe/Mo ions disorder. Electrical resistivity of the sample exhibits a semiconductor behavior, which can be well understood by variable-range hopping model. A maximum magnetoresistance effect value about 15% was observed at 20 K and 70 kOe. The pronounced linear magnetoresistance effect is attributed to the suppression of spin-fluctuations by the magnetic field.

Polycrystalline layered perovskite Sr2CoO4 sample was synthesized by high temperature and high pressure method. The staircaselike behavior has been observed in the magnetization and resistivity versus field curves of Sr2CoO4 at low temperature. The main features of the steps can be obtained from the measured results: (i) the positions of the external magnetic field at which steps occur are varying in different measurement runs, (ii) the steps only appear at low temperature and disappear with a slight increase of the temperature, (iii) the steps are dependent on the temperature and field sweep rate. Based on the features of the magnetization and magneto-transport staircaselike behavior in Sr2CoO4, the unusual phenomenon can be ascribed to an avalanche of flipping domains in terms of the random field theory.