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Abstract: We have investigated the hyperfine interaction in Co2SiO4 by inelastic neutron scattering with a high resolution back-scattering neutron spectrometer. The energy spectrum measured from a Co2SiO4 powder sample revealed inelastic peaks at at T=3.5K on both energy gain and energy loss sides. The inelastic peaks move gradually towards lower energy with increasing temperature and finally merge with the elastic peak at the electronic magnetic ordering temperature . The inelastic peaks have been interpreted to be due to the transition between hyperfine-split nuclear level of the 59Co isotopes with spin . The temperature dependence of the energy of the inelastic peak in Co2SiO4 showed that this energy can be considered to be the order parameter of the antiferromagnetic phase transition. The determined hyperfine splitting in Co2SiO4 deviates from the linear relationship between the ordered electronic magnetic moment and the hyperfine splitting in Co, Co–P amorphous alloys and CoO presumably due to the presence of unquenched orbital moment. These results are very similar to those of CoF2 recently reported by Chatterji and Schneider [7]. [Copyright &y& Elsevier]

Abstract: In this paper we report the study of the perovskites La0.7Ca0.3Mn0.5Co0.5O3 and La0.8Sr0.2Mn0.5Co0.5O3 by neutron powder diffraction at various temperatures and magnetization measurements in zero applied field and at low cooling regimes. The replacement of half Mn by Co in La0.7Ca0.3MnO3 and La0.8Sr0.2MnO3 destroys their long-range ferromagnetism exhibiting a cluster glass ferromagnetic order similar to the one observed in many cobaltites. [Copyright &y& Elsevier]

Abstract: The effect of pulsed electron irradiation on the long- and short-range order in the La0.7Sr0.3CoO3 ceramics is reported. Neutron and X-ray powder diffraction reveal that the unit cell symmetry and single-phase state of single and multiple irradiated La0.7Sr0.3CoO3 are preserved, while the oxygen atoms coordination changes towards the La0.5Sr0.5CoO3 structure. X-ray absorption data confirm this observation and further reveal the details of the shift and splitting of the Co3+ t2g and eg atomic orbitals. Possible mechanisms of pulsed electron irradiation effect in La0.7Sr0.3CoO3 are discussed. [Copyright &y& Elsevier]

The crystal and magnetic structures of layered perovskites TbBaCo2-xFexO5+γ (0.08⩽x⩽0.24) were studied by neutron powder diffraction. Increasing iron concentration up to the x values higher than 0.10 leads to the orthorhombic→tetragonal phase transition resulting from the transformation of 2×1×1-type superstructure, formed due to ordering of extra oxygen incorporated into the vacant sites in [TbOγ] layers, into 3×3×1 superlattice. The concentration ranges, where the orthorhombic and tetragonal lattices exist, are separated with a narrow two-phase domain. For the tetragonal phases with 3×3×1 superstructure (space group P4/mmm), the Co/Fe ions are antiferromagnetically coupled, forming G-type spin-ordered configuration. The Co3+ cations located in square-pyramidal sites adopt intermediate spin state, whilst a relatively small magnetic moment of Co3+ ions in the octahedral sublattice indicates that a minor fraction of cobalt is in the low-spin state. [Copyright &y& Elsevier]