Structure, spin glass, and spin state in perovskite GdCo/sub 1-x/Mn/sub x/O/sub 3/ (x /spl les/ 0.5)
Perovskite GdCo/sub 1-x/Mn/sub x/O/sub 3/ (x=0.2,0.3,0.4,0.5) compounds have been prepared by solid-state reaction. Structures were characterized using X-ray diffraction and Rietveld Refinement method. The compounds crystallized in orthorhombic with Plmn space group. Crystal lattices decreased with the increase of Mn doping level. DC magnetization and ac susceptibility were studied over a wide temperature range and different frequencies. A typical spin glass state was observed in all samples around the same temperature of 122 K where the compounds turned from paramagnetic to ferromagnetic states. For x<0.5, secondary transitions were observed both in dc and ac measurement which were independent of frequency but depended on doping level. The valences of Co or Mn with possible spin states were estimated.
Structures, and far-infrared and Raman spectra of GdMn1 − xCoxO3 (x = 0–1.0)
Abstract We report the structural and optical properties of the perovskite GdMn 1  −  x Co x O 3 ( x  = 0–1.0) compounds. Far-infrared (FIR) and Raman spectroscopy measurements were carried out at room temperature. The FIR spectra show four vibration modes at ∼ 190, ∼ 250, ∼ 400, and ∼ 600 cm − 1 that correspond to external, torsional, bending, and stretching modes, respectively. It was found that the FIR active vibration energies exhibit splitting and shifting as the Co doping level increases. The Raman spectra reveal that the most intense spectral feature in the GdMnO 3 is at 612 cm − 1 , which shifts to higher and lower energies, depending on the Co doping level.
Magnetic interactions in the system (La, Gd)2CoMnO6
Abstract Magnetic susceptibility measurements are reported on gadolinium substituted mixed perovskites of the composition La2−xGdx(CoMn)O6. The results are found to be more in favour of the earlier finding of ferromagnetic Mn3+−02−−Mn3+ interactions in La2CoMno6, with diamagnetic low-spin Co3+ ions, than the electronic configuration Co2 + −O2−−Mn4 + recently reported. The samples with x = 0·5 and 1·0 exhibited maxima in the magnetization curves at low temperatures, similar to HoFeo3, indicating antiferromagnetism. It is considered likely that the Gd-Co, Mn interaction induces a complicated non-collinear spin arrangement with a postulated spin canting in the rare earth sub-lattice.