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Iron sand is one of the natural resources in West Sumatra that has not been optimally utilized. One of the potential locations to get this iron sand deposits is the coast of Kata. This study aims to analyze the content and size of the iron grains found on the coast of Kata Padang Beach, West Sumatera Province. Coastal sand samples are extracted using permanent magnets to separate magnetic and non-magnetic materials. Characterization of iron sand using Scanning Electron Microscopy with Energy Dispersive X-ray (SEM-EDX) and Vibrating Sample Magnetometer (VSM). The result of characterization using SEM-EDX shows that iron sand samples contain Fe and O elements derived from Phase Magnetite (Fe3O4).  Keywords: iron sand, magnetic materials, SEM-EDX, VSM

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Magnetic nanoparticles of cobalt ferrite (CoFe2O4) have been synthesized by co-precipitation method with various synthesis temperatures, concentration of NaOH and stirring duration. The results showed that nanoparticles have well crystallized structure with various grain sizes which depend on synthesis parameters. The grain size increased with increasing synthesis temperature, decreasing concentration of NaOH and decreasing stirring duration. Magnetic characterization of CoFe2O4 nanoparticles measured by Vibrating Sample Magnetometer (VSM) showed that coercive field was decrease with the decreasing of particle size. The saturation and remnant magnetization showed increasing when crystallinity increased. However, it also depends on presence of α-Fe2O3 phases and their grain size. Based on magnetic characterization analysis, sample with parameter of synthesis temperature 80°C, concentration of NaOH 5 M and stirring duration 120 minutes have been selected to be modified using polyethylene glycol (PEG)-4000. XRD and TEM analysis showed that surface modification with PEG-4000 could increase the crystallinity of nanoparticles, decrease agglomeration and control the shape to more spherical. VSM analysis showed that modification PEG-4000 could decrease the saturation magnetization which is due to the existence of α-FeO(OH) and γ-FeO(OH) phases from bonds at interface of CoFe2O4 as confirmed by XRD and Furrier Transform Infra Red (FTIR) analysis. Keywords: magnetic nanoparticles, CoFe2O4, copresipitation, PEG-4000