Investigation of ac magnetic properties of magnetite obtained from Cox,s Bazar beach sand

Abstract

In Bangladesh, Cox's Bazar beach sand contains potentially valuable minerals as discovered during a geological survey for radioactive minerals in 1961. Beach sand contains magnetic materials in the form of magnetite. Beach sand was collected from Kolatoli sea beach; Cox's Bazar, was washed by water to separate other unnecessary materials such as small rock, clay, etc. Afterward, the sand was dried and fmally separated by strong magnet, Obtained magnetite powders were gronnd by ball milling for several hours in water media. The coarse particle fractions were eliminated by sedimentation. The raw powders are then sintered at 750°C and 900°C for I h. X-ray diffraction studies show that the raw powders sintered at 750°C is the best samples. From this dried fine powder of magnetite toroid and disk-shaped samples were prepared by uniaxial pressing and sintered at various temperatures for various dwelt times. Structural, DC and AC magnetization, and electrical transport properties of these sintered magnetites were investigated thoroughly. X-ray diffraction studies show that the magnetite forms spinel structure with some impurities. It was observed that the magnetite separated from beach sand shows Verwey transition at 125 K. The sinterectmagnetite has highest magnetization about 3.5 j.lB which is about 88% magnetization value of the pure magnetite. Real part of the initial permeability,.u:, also varies with sintering temperature and sintering time. For a fixed sintering temperature, it is observed that .u: values increases as the sintering time increase, perhaps due to improved microstructure. Utilizing magnetite from the beach sand and commercially available Zno, the Fe].,Zrtx04 (x = 0.30 and 0.5) ferrites were prepared by a conventional solid state reaction technique. The samples were sintered at 750°C in air for I h. Structural investigation of these ferrites was studied by x-ray diffraction. It was observed that the lattice parameter increases as the Zn content increases, which obey the Vegards law. The DC and AC magnetic properties are aillo investigated using SQUID magnetometer and Impedance Analyzer, respectively. It was observed that the magnetization values fall drastically due to the substitution of In. This result can be explained with the help of cation distribution in the A-site and B-site in the spinel structure. However, the real part of the permeability increases and loss factor decreases due to Zn substitution in magnetite.