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Effect of reducing agent and surfactant on the morphology, structural and magnetic properties of Ni magnetic nanoparticles

ABSTRACT We report the effect of reducing agent and surfactant on the morphology, structural and magnetic properties of Ni magnetic nanoparticles (MNPs) synthesised by the polyol process. The samples in this work were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometry (VSM). The XRD results indicate that samples synthesised by EG-NaOH and 1.2H-OAm/OAc have a cubic structure with space group Fm- m. The average crystallite sizes of these samples are found to be ∼ 20.7 and 16.2 nm, respectively. The sample synthesised by a combination of EG-OAm/OAc grows in nanorod form, whereas that synthesised by EG-NaOH and 1.2H-OAm/OAc has a spherical shape. The temperature dependence of the magnetisation, (M-T) measurements, indicate that the EG-NaOH sample has a superparamagnetic transition, while the 1.2H-OAm/OAc sample shows ferromagnetic behaviour in the temperature range of 5–380 K. The magnetic anisotropy constants of the EG-NaOH and 1.2H-OAm/OAc samples extracted from the M-T experiments, are 141.3 × 105 and 10.5 × 105 erg/cm3, respectively. In addition, the magnetic hysteresis measurements taken at 5 and 300 K show that the 1.2H-OAm/OAc sample is more stable than the sample synthesised by EG-NaOH. The overall results are important for the use of the Ni MNPs for low- and room-temperature applications in bio- and nano-technology.