Studies on Processing and Characteristics of Iron Carbides

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In this research, the processing and the characteristics of iron carbides particles and films were investigated in detail in order to elucidate the basic properties for their application to a magnetic recording material.CO gas diluted with N_2 was found to be a very effective reactive gas for carburization of iron oxides or alpha-Fe to produce the well-defined iron carbides. Fe_5C_2 formed as a major phase at temperatures from 300 to 400^ﾟC. Fe_3C could be synthesized above 400^ﾟC as a single phase. The addition of alkali or alkaline earth to iron oxide particles was found to be a key to synthesize Fe_7C_3 particles.The improvement of the coercivity and the squareness of the magnetic characteristics could be achieved by the processing of acicular Fe_3C particles, which were synthesized from acicular alpha-Fe particles with CO gas. Their saturation magnetization, the coercivity and the squareness were 100 emu/g, 700 Oe and 0.4, respectively.Fe_3C thin films could successfully be synthesized by the controlled RF-magnetron sputtering with a composite target of Fe/C. The optimum condition to synthesize the single phase Fe_3C films found to be as follows ; temperature, 350^ﾟC, Ar pressure, 5 Pa.The saturation magnetization and the coercivity of the Fe_3C films were from 100 to 120 emu/g and 250 Oe, respectively, The films exhibits a longitudinal magnetization direction.