Magnetic Behavior of Iron-Rich Permalloy Nanoparticles
Iron-rich permalloy Fe{sub x}Ni{sub 1−x} nanoparticles (NPs) were fabricated using a low-temperature wet chemistry method involving the hydrothermal growth of the NPs. Three Fe–Ni NPs (Fe{sub 0.5}Ni{sub 0.5}, Fe{sub 0.625}Ni{sub 0.375}, and Fe{sub 0.83}Ni{sub 0.17}) were fabricated and studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM). After the initial formations, the three Fe–Ni NPs were annealed at 200, 400, and 600 °C; the XRD showed that all three FeNi NPs had a bcc structure (not the fcc structure of the standard Fe{sub 20}Ni{sub 80} permalloy). The SEM images showed that the NPs had spherical shapes. The VSM measurements showed that none of the Fe–Ni nanoparticles were superparamagnets but were ferromagnets. The heat treatments cause the work needed to the flip the spin (coercivity (H{sub c})) to increase and the values of the saturation magnetizations to fluctuate.