Influence of thermal treatment on the magnetic properties and morphology of electrodeposited Fe-Co films

Abstract

Fe-Co films were prepared by electrodeposition from an electrolyte containing citric acid and annealed afterwards at different temperatures up to 700 °C. The grain sizes of the deposits increased from 11 nm to 30 nm with increasing annealing temperature, which lead to changes in magnetic properties of deposits. SQUID measurements indicate that there is a difference between the coercive force, Hc, of the as deposited samples (17 Oe) and the heat-treated samples (25–40 Oe) with a measurement error of 1–2 Oe. The remnant magnetization, Mr, decreased from 190 ± 12 emu/cm3 for the as deposited to 75 ± 5 emu/cm3 for the annealed samples, respectively. The saturation magnetization, Ms, seems not to be influenced strongly by the thermal treatment, with the only exception for the samples annealed at 500 °C. Thus, Ms has a slightly decreasing tendency from 1880 ± 90 emu/cm3 for the as-deposited samples to 1780 ± 85 emu/cm3 for samples annealed at 700 °C. The biggest value for Ms (2100 ± 105 emu/cm3) was obtained if the samples were annealed at 500 °C. The thermal treatment generated cracks in the deposits. Interestingly, these cracks had a regular rectangular shape only if the deposits were annealed at 600 °C. The coercivity of the layers annealed at 600 °C was lower compared to layers annealed at the other temperatures. Magnetic force microscopy measurements indicated the magnetic domain distribution and the topography of the annealed deposits. The deposits showed the best soft magnetic properties if annealed between 500 and 600 °C.