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Abstract: M-type barium hexaferrites Ba1−x Ce x Fe12−x Co x O19 () have been synthesized by a simple chemical coprecipitation method. X-ray diffraction (XRD) studies indicate that the samples are of single phase, with space group . The results of field-emission scanning electronic microscopy (FE-SEM) show that the grains are regular hexagonal platelets with sizes from 0.5 to . It is observed that the value of the coercivity field () increases at low substitution (), reaches a maximum at , and then decreases at , while the value of saturation magnetization () decreases monotonically with increasing . The variations of magnetic properties can be tentatively attributed to the effects of Ce–Co substitution. The results above indicate that our samples might be promising candidates for permanent magnets and perpendicular recording media materials in the future. [Copyright &y& Elsevier]

Abstract: Mn-substituted Bi0.8Ca0.2FeO3 ceramics Bi0.8Ca0.2Fe1−x Mn x O3 (0≤ x ≤0.5) were synthesized by a solid-state reaction method. Powder X-ray diffraction investigations performed at room temperature show that the crystal structure is rhombohedral for x ≤0.1 and orthorhombic for 0.2≤ x ≤0.5. Compared to the undoped Bi0.8Ca0.2FeO3 compound, enhanced magnetization and electric polarization were observed in the samples with x ≤0.1. A further increase in the magnetization with increasing x took place in the samples with 0.2≤ x ≤0.5. All the Mn-substituted samples studied are basically antiferromagnetic accompanied by the appearance of weak ferromagnetism, which is similar to the BiFeO3 compound. The conductivity of the samples with x ≥0.3, measured between 140 and 380K, is of the semiconducting type. [Copyright &y& Elsevier]

Abstract: La0.7Sr0.3MnO3 nanoparticles were prepared by a simple chemical coprecipitation route. Structural, magnetoresistance (MR), and magnetic properties were investigated. Rietveld refinement of X-ray powder diffraction result shows that the sample is single-phase with the space group of R3¯C. The result of field-emission scanning electronic microscopy shows that most of the grain sizes are distributed from 50 to 200nm. The composition determined by energy-dispersive spectroscopy is the stoichiometry of La0.7Sr0.3MnO3. The ferromagnetic to paramagnetic transition is sharp with Curie temperature T C=367K, which further confirms that the sample is single-phase. The steep change in MR at low fields is attributed to the alignment of the magnetization, while the high-field MR is due to the grain boundary effect. [Copyright &y& Elsevier]

Abstract: M-type strontium hexaferrite (SrFe12O19) particles had been prepared by a modified chemical co-precipitation route. Structural and magnetic properties were systematically investigated. Rietveld refinement of X-ray powder diffraction results showed that the sample was single-phase with the space group of P63/mmc and cell parameter values of a=5.8751Å and c=23.0395Å. The results of field-emission scanning electronic microscopy showed that the grains were regular hexagonal platelets with sizes from 2 to 4μm. The composition determined by energy dispersive spectroscopy is the stoichiometry of SrFe12O19. The ferrimagnetic to paramagnetic transition was sharp with Curie temperature T C=737K, which further confirmed that the samples were single phase. However, it was found that the coercivity, saturation magnetization and the squareness ratio of the synthesized SrFe12O19 samples were lower than the theoretical values, which could be explained by the multi-domain structure and the increase of the demagnetizing factor. [Copyright &y& Elsevier]

Abstract: Sr2FeMoO6 samples with different grain sizes were prepared by the sol–gel method. X-ray diffraction (XRD) patterns and field-emission scanning electron microscopy (FE-SEM) of the Sr2FeMoO6 samples show that the samples are in the nanometer range. The average grain sizes for these samples are 34.5, 39.7 and 44.3 nm, increasing with the sintering temperature. The transport measurements show that the Sr2FeMoO6 samples behave like semiconductors at low temperatures, dominated by the carrier scattering at the grain boundaries (GBs). And the resistivities of the samples are 1.6, 1.2 and 0.5 mΩ cm at 10 K, respectively, increasing with decreasing grain size. The temperature dependences of the magnetization and resistance clearly demonstrate the coexistence of ferromagnetic metal and antiferromagnetic (or paramagnetic) insulator, which is believed to induce a metal–insulator transition at the Curie temperature . [Copyright &y& Elsevier]

Abstract: Y Fe0.5Cr0.5O3 ceramics have been synthesized by a conventional solid-state reaction. Powder X-ray diffraction shows that this compound possesses an orthorhombic structure with Pnma space group. It exhibits a high magnetic transition temperature at around 250 K with weak ferromagnetic behavior below this temperature. A dielectric relaxation following the Arrhenius law found in the Y Fe0.5Cr0.5O3 compound can be attributed to the charge carrier hopping conduction. [Copyright &y& Elsevier]