Composition Gradients and Magnetic Properties of 5–100 nm Thin CoNiFe Films Obtained by Electrodeposition

Abstract

The composition gradient and properties of magnetic 5-100 nm thin CoNiFe films electrodeposited on Cu or Pt substrate were studied. It was found that the average elemental composition of CoNiFe, obtained by ICP analysis, changes during electrodeposition. The extent of anomalous co-deposition achieved at deposit thickness <100 nm was found to be several times larger than in thicker CoNiFe films. The partial current densities for all three metals (Co, Ni, Fe) increase during the time of electrodeposition and gives rise to stable value when the thickness reaches about 100 nm. The partial current density for hydrogen evolution decreases and becomes stable at the thickness >100 nm. The observations related to the experimental results could be explained through a modified Bockris-Drazic-Despic reduction mechanism. The time-dependent dynamics of roughening surface exhibits two characteristic regions, i.e. the first with fast roughening at the thickness <100 nm and the second with slow roughening at the thickness >100 nm. The stress evolution show typical compressive-tensile-compressive behavior in the thickness range 5-100 nm. The crystal structure of 20 nm CoNiFe films is mixed fcc + bcc crystallites with the larger grain size close to the substrate while thick films show fcc-rich structure. The mechanism of coercivity in CoNiFe films is governed by magnetoelastic anisotropy and follows Neel's thickness dependence relation, i.e. H c = c t −n . The "volcano" type of H c -t curve obtained at 5-50 nm was explained taking into account: change of composition, stress, crystal structure and roughness.

Potentiostatic Electrodeposition of Co-Ni-Fe Alloy Particles Thin Film in a Sulfate Medium

“…In this study, it was revealed that the use of ITO as the substrate led to the formation of amorphous phase, which agreed well with the findings of other workers [36,37]. However, the use of copper substrate for example, can yield crystalline phase of the deposits [38,39]. The amorphous phase is suitable for super capacitor application, as proton can easily permeate through the bulk of the electrode materials where the whole electrode can be utilized for energy storage [40].…”

Influence of Surface Roughness and Current Efficiency on Composition Gradients of Thin NiFe Films Obtained by Electrodeposition

“…14 We report here that the concentration gradient in 5-500 nm thin NiFe films is related to the dynamics of the surface roughening and changes in current efficiency during the early stages of deposition.…”

“…13,14 For the application of thin magnetic film with thickness <200 nm, the composition gradient would be detrimental in controlling of magnetic properties. It had been shown earlier 9,10 that the composition in NiFe films is stabilized more quickly in the case of pulse electrodeposition compared to galvanostatic electrodeposition.…”

In-depth component distribution in electrodeposited alloys and multilayers

“…Historically, the spontaneous variation of the alloy composition during d.c. plating was detected as the change of the average composition as a function of the thickness [10][11][12][13][14]. Although this procedure is well indicative of a composition change, it is an integral method, which also means that its sensitivity to either local effects or subtle changes is very little.…”