Abstract
Materials based on Ni-Co-Fe alloys, due to their excellent magnetic properties, attract great attention in nanotechnology, especially as candidates for high-density magnetic recording media and other applications from spintronic to consumer electronics. In this study, Ni-Co-Fe nanocrystalline coatings were electrodeposited from citrate-sulfate baths with the Ni2+:Co2+:Fe2+ ion concentration ratios equal to 15:1:1, 15:2:1, and 15:4:1. The effect of the composition of the bath on the morphology, microstructure, chemical composition, microhardness, and magnetic properties of the coatings was examined. Scanning (SEM) and transmission (TEM) electron microscopy, X-ray diffractometry (XRD), and energy dispersive X-ray spectroscopy (EDS) were used to study surface morphology, microstructure, chemical, and phase composition. Isothermal cross-sections of the Ni-Co-Fe ternary equilibrium system for the temperature of 50 °C and 600 °C were generated using the FactSage package. Magnetic properties were analyzed by a superconducting quantum interference device magnetometer (SQUID). All the coatings were composed of a single phase being face-centered cubic (fcc) solid solution. They were characterized by a smooth surface with globular morphology and a nanocrystalline structure of grain diameter below 30 nm. It was determined that Ni-Co-Fe coatings exhibit high hardness above 4.2 GPa. The measurements of hysteresis loops showed a significant value of magnetization saturation and small coercivity. The microstructure and properties of the obtained nanocrystalline coatings are interesting in terms of their future use in micromechanical devices (MEMS).
Highlights
Electrodeposition of nanostructured materials plays an essential role in nanotechnology
The chemical composition of the coatings obtained in our study was in good agreement with the results of Zhang et al [29], who observed that in most examined conditions, Fe ions reduced at a higher rate than Co ions
Our results showed that the increase in Co content in ternary alloys caused a significant rise in Ms due to the replacement of some of Ni atoms by Co atoms, characterized by a higher magnetic saturation
Summary
Electrodeposition of nanostructured materials plays an essential role in nanotechnology. Binary Co-Fe alloys show the highest magnetic flux density among the alloys of the iron group, reaching over 2.4 T, and exhibit high magnetic coercivity, high internal stresses, brittleness, and poor corrosion resistance [1]. The improvement of their properties might be carried out by the addition of alloying elements such as Ni or Cu [1,2]. Thin coatings obtained by electrodeposition are characterized by low surface roughness, nanocrystalline structure, and often better corrosion and mechanical properties than bulk materials
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