Electrodeposition of nano-grain sized Bi–Co thin films in organic bath and their magnetism

In this paper we report the preparation of nano-grain sized Bi1−xCox thin films containing different percentages of bismuth and cobalt by galvanostatic electrodeposition on Cu substrates in organic baths, and provided a good procedure to prepare nano-grain sized Bi-based alloy thin films. The prepared Bi1−xCox thin films consisted almost entirely of nanograins with sizes of 20–80 nm, and they were very compact. The results of X-ray diffraction (XRD) indicated that the nano-grain sized Bi1−xCox thin films were amorphous. After heat treatment of crystallization at 280 °C for 1 h in a protecting atmosphere, Bi(110), Cu(111), Bi10Co16O36(532), Co(102) and Co(110) phases could be found in XRD patterns, respectively. The magnetic measurements showed that the nano-grain sized Bi1−xCox thin films had a superparamagnetism-like behavior with the magnetization increasing rapidly and then reaching saturation, and a clear enlargement of deposit coercivity was obtained by increasing Co content.