Mingxiang Xu

Heat-induced changes in microstructure and magnetic properties of Co0.75Ni0.75[Fe(CN)6] · XH2O

Polycrystalline Co0.75Ni0.75[Fe(CN)6] · XH2O was prepared by coprecipitation. The coprecipitated powder was annealed in vacuum at 80°C, 100°C, and 130°C. Variation of microstructural and magnetic properties with different annealed temperatures was studied by Fourier-transform infrared, X-ray diffraction, and magnetization measurements. The differences in magnetic phase transition temperature, coercivity, remanence, and effective magnetization were studied in detail. The magnetic contribution mainly results from FeIII–CN–CoII/NiII and FeIII–NC–CoII/NiII because FeII–CN–CoIII/NiII carries no net spin. After annealing at 130°C, the microstructures FeIII–CN–CoII/NiII and FeIII–NC–CoII/NiII convert to FeII–CN–CoIII/NiII. Differences in magnetic properties may be attributed to heat-induced microstructural changes.

Charge–transfer-induced spin transition in K0.28Co1.36[Fe(CN)6] · XH2O with different annealing temperatures

The Prussian blue analog K0.28Co1.36[Fe(CN)6] · XH2O was prepared by standard chemical co-precipitation. The precipitate was filtered and dried in a vacuum oven at room temperature, 80°C, and 120°C. The powder X-ray diffraction measurement indicates a typical face-centered cubic pattern. The diffraction peaks show a slight shift to higher angle with increasing annealing temperatures, a signature of lattice contraction, which is mainly related to the inner charge transfer from FeIII to CoII. The value of χ · T is variable and dependent on temperature. The temperature dependence of χ −1 shows a large deviation from the Curie–Weiss law. The behavior could result from a charge-transfer-induced spin transition. Isothermal magnetization curves also suggest that the inner charge-transfer spin transition depends on the annealing temperature.

Temperature and ultraviolet irradiation effect in BLT thin films

With the significant innovation and rapid development of the nonvolatile ferroelectric random access memory devices (FeRAMs), many efforts have been done to research and develop the ferroelectric films. Bismuth layer-structured ferroelectrics, such as lanthanum-doped bismuth titanate, have been paid a lot of attentions for their super properties. Temperature and ultraviolet irradiation, two of the important factors which can affect the properties of films, have been attracted much attention. In this paper, we mainly investigated the annealing temperature and the ultraviolet irradiation effect on the ferroelectric properties of Bi3.25La0.75Ti3O12 (BLT) thin films.

Heat-induced magnetic properties changes of Mn 3 [Fe(CN) 6 ] 2 ·XH 2 O

In this paper, we report a study on heat-induced magnetic properties changes of Mn3[Fe(CN)6]2·XH2O. Molecular magnet nickel(II) hexacyanoferrate(III) powder Mn3[Fe(CN)6]2·XH2O was prepared by coprecipitation method. The coprecipitated powder was annealed in vacuum at different temperatures of 80, 100, 130, and 150°C. Variation of magnetic properties with different annealed temperatures was studied by elemental analysis, powder X-ray diffraction, Fourier-transform infrared, Mossbauer and magnetization measurements. From the elemental analysis, we can know the powders annealed at the different temperatures have the chemical composition of Mn3[Fe(CN)6]2·XH2O. The compounds at the different temperatures are characterized by two intense peaks, 2070 and 2149 cm-1, which can be assigned to v(FeII-CN-MnIII) and v(FeIII-CN-MnII) respectively. The line broadening and position found in the XRD peaks of the four samples are all but the same. This suggested no microstructural changes after the annealing at the different temperatures. By using Sherrers equation: D = kλ/βcosθ, where λ is the X-ray wavelength, β the half-peak width, θ the Bragg angle in degrees, and k the shape factor often assigned a value of 0.89, the average sizes of all the samples were estimated to be about 10 nm. Mossbauer measurements show that the FeII-CN-MnIII bond is formed in the annealed samples.

The magnetic properties of p-type Zn 1−x Mn x O achieved by co-precipitation technique

In this paper, the magnetic properties of p-type Zn_1-xMn_xO powders are reported. This are prepared from the decomposition of an oxalate precursor Zn_1-xMn_xC₂O₄^.H₂O. The oxalate precursor is obtained by coprecipitation of 50 ml of a 0.4mol/L aqueous solution of Zn and Mn acetates and the same volume of a 0.4 mol/L solution of oxalic acid. The mixed solution is stirred for 2h at room temperature. We added CH₃COONH₄ and In(NO₃)₃^.H₂O as p-type doped source (Zn:N:In=l:3:0.05 mol) to the solution with addition 3h stirring. The precipitate is then washed with distilled water and dried in air. The white powders obtained are then annealed in N₂ at 500-800 K for 2h and finally turned moss yellow powder samples. The structure of the powder samples are studied by X-ray diffraction (XRD). All the observed lines from the XRD patterns show the ZnO structure without any hint of an impurity phase. With the increase of x, the peak position of Zn_1-xMn_xO shifts towards lower angles and the lattice constants a and c increase linearly, which means that the Mn²⁺ replaces well the Zn²⁺ to occupy the 2b crystallographic site.