A series of Ni(1−x)FexO (x=0, 0.015, 0.03, 0.05, and 0.1) bulk samples was synthesized by the chemical concentration-precipitation method. Phase composition analysis was carried out, which showed that trace amounts of ferromagnetic phase NiFe2O4 could not be detected by x-ray diffraction in these bulk samples with x≤0.03. When x>0.03, NiFe2O4 ferrite is detected easily. The magnetic properties of all the bulk samples were investigated by measuring their magnetization as a function of temperature and magnetic field. The results indicated that all the bulk samples sintered in air exhibited large room-temperature ferromagnetic behavior ascribed to a ferromagnetic impurity phase. Simultaneously, an exchange bias and training effect were also observed in all the bulk samples, suggesting the possibility of the existence of a strong ferromagnetic/antiferromagnetic exchange coupling in this kind of compound. Specifically, the exchange bias field could be tuned by changing the concentration of the Fe dopant.

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The long and short range order of chemically prepared Co2FeGa Heusler nanoparticles with various sizes are determined by x-ray diffraction (XRD) and extended x-ray absorption fine structure (EXAFS) spectroscopy. Specifically, EXAFS fittings reveal the size dependent crystal structure and short range order of the Heusler type Co2FeGa nanoparticles. With decreasing particle size, the degree of L21 order in the nanoparticles decreases and the probability of B2 disorder increases simultaneously. The consequences of antisite disorder on the size correlated structure of Co2FeGa nanoparticles are also discussed.

Spinel zinc chromite nanocrystals with various grain sizes ranging from 6.8 to 32 nm have been synthesized using a formalin sol–gel method. Samples were characterized by x-ray diffraction, transmission electron micrograph, and superconducting quantum interference device magnetometer. An effect of particle size on magnetic properties is observed. The decrease in particle size leads to a large enhancement of magnetization. Antiferromagnetic transition disappears when the particles reach a critical size, which can be explained by the deviation from the normal spinel structure in the cation distribution induced by particle size.