The spin ladder compounds Sr14Cu24O41+δ were synthesized by conventional solid state reaction method with subsequent annealing at 400, 500, 600, 800 and 900 ℃, respectively. The energy dispersive spectroscope (EDS) measurement confirms that the content of oxygen in the samples decreases with the increasing of annealing temperature. The measurement of magnetic susceptibility reveals that the sample annealing at 600 ℃ has the largest number of dimers. The measurement of Raman spectrum shows some new Raman vibrational features. Corresponding to δ>0 or δα=cl/cc is near the minimal value 10/7 and the Cu—O bond has relatively long length.

Polycrystalline samples of Sr14Cu24O41 and Sr14（Cu0.97M0.03）24O41（M=Zn, Ni, Co） were synthesized by standard solid state reaction method. All samples are single phase as identified by X-ray diffraction, no regular shift of lattice parameters a, c is found, but the lattice parameter b increases slightly with doping magnetic ions Ni and Co, and has no change with doping non-magnetic ion Zn, respectively. Selected area electron diffraction experiments show that Zn,Ni and Co ions may substitute for Cu ions in the chain. All the doping compounds are still semiconductors and have a crossover temperature Tρ like the parent phase Sr14Cu24O41. The influence of magnetic ion Ni or Co doping on the resistivity is smaller than that of non-magnetic ion Zn doping, while the influence of non-magnetic ion Zn doping on crossover temperature is smaller than that of magnetic ion Ni or Co doping.

We have investigated the Fe/Cr doping effects on the magnetic property of a charge-ordered antiferromagnetic manganite La0.4Ca0.6MnO3. Magnetic measurements reveal interesting doping effects. While all the Fe-doped samples still have antiferromagnetic ground state, strong ferromagnetic tendency can be seen in the Cr-doped samples. Meanwhile, Cr-doped samples show clear metallic transport behavior, indicating an inherent double exchange mechanism responsible for the ferromagnetic metallic state. We thus propose that the magnetic exchange interaction between Mn and dopants, and the d-orbital electronic structure of Cr/Fe are essential for the distinct doping effect of Fe and Cr.

In this paper, polycrystalline BaFe4-xTi2+xO11 (x=0, 0.25, 0.5, 0.75, 1) samples have been synthesized by the conventional solid-state reaction method. X-ray diffraction (XRD) patterns of all the samples show that the diffraction peaks correspond to that of an R-type hexagonal ferrite structure, and no trace of second phase is detected. Measurement of X-ray photoelectron spectroscopy (XPS) reveals that most of the Fe ions in BaFe4Ti2O11 are trivalent and the fitting of two peaks in Fe 2p spectrum corresponding to different Fe ion sites, while the amount of Fe2+ ions increases with the increase of Ti ions in BaFe4-xTi2+xO11. The spectroscopy of Ti ions confirms that the valence of Ti in BaFe4-xTi2+xO11 are tetravalent. Magnetic susceptibility of BaFe4-xTi2+xO11 (x= 0, 0.25, 0.5, 0.75, 1) reveals two magnetic transitions at T1～250 K and T2～83 K, which indicate a complex magnetic order driven by competing interactions on a frustrated lattice with a noncentrosymmetric structure. For all the samples, the magnetic susceptibility obeys Curie-Weiss law above T1, and M-H curves exhibit a linear variation with magnetic field in this temperature range, which is consistent with the paramagnetic behavior. A decrease of the effective magnetic moment is due to the increase of Fe2+ ions with the increase of Ti content in BaFe4-xTi2+xO11. Below T1, the magnetization curve as a function of temperature (M-T) and the magnetization versus magnetic field (M-H) at different temperatures imply its characteristic of a typical canted antiferromagnetic or ferrimagnetic state. Meanwhile, the transition temperature T2 drops gradually with the increase in Ti content, which might be related to the change of occupying of Fe ions in the kagome layers.