Studies of electrical resistivity and magnetic properties of nanocrystalline CoFeCu thin films electrodeposited from citrate-added baths

Abstract

In this study, nanocrystalline CoFeCu thin films were electrodeposited at different current densities from baths with natural pH (around 5.2) and containing 20 g/L citrate sodium. The relationship of films structure with soft magnetic properties and electrical resistivity, which are required for new generation magnetic head core, were investigated. SEM, EDS, XRD, TEM, VSM and four probe-point methods were used for characterization of the deposited films. The deposited films exhibited very uniform and homogenous structure with co-axis grains (confirmed by (111) and (110) poles figures and TEM images) throughout the coating. Overall, it was noticed that increasing current density from 1 to 24 mA/cm 2 reduced both grain size (from 63 to 8 nm) and coercivity (from 20 to 1 Oe) of the films. In addition, plotting Log (Hc) versus Log (D 6 ) demonstrated that the coercivity of the films followed ''D 6 law''. Moreover, increasing current density changed phase structures of the films from FCC (Cu)?FCC (Co) to FCC (Co) and then to FCC (Co)

The influence of deposit composition controlled by changing the relative Fe ion concentration on properties of electroplated nanocrystalline Co-Fe-Cu ternary thin films

“…Additionally, there is no reflection from the diffraction peak of the bcc phase structure of Fe in the XRD patterns of the deposits with low Fe contents of 4.1 at.% and 7.8 at.%, as can be seen from Figures 4a and 4b, respectively. Similarly, no reflection from the diffraction peak of the bcc phase structure of Fe was observed in previous studies carried out with electrochemically deposited Co-Fe-Cu ternary films when the Fe content within the films was lower than 11 at.% [4] and 14 at.% [8]. As a result, we reveal that the phase structure changes from a mixture of hcp Co and fcc/hcp Co to a mixture of fcc/hcp Co and bcc Fe with increasing Fe content within the films, as also summarized in Table 1.…”

“…On the other hand, the absence of fcc Cu peaks in all XRD patterns can probably be attributed to the low Cu content within the films (about 3 at.%). In a previous study, the reflection from the fcc Cu diffraction peak was not observed when the Cu content was lower than 15 at.% [4]. Additionally, there is no reflection from the diffraction peak of the bcc phase structure of Fe in the XRD patterns of the deposits with low Fe contents of 4.1 at.% and 7.8 at.%, as can be seen from Figures 4a and 4b, respectively.…”

“…On the other hand, as can be seen from Figure 1, an increase in the cathode potential with increasing relative Fe ion concentration may also lead to a decrement in the mean size of the crystallites. It was reported in previous studies that the mean size of the crystallites decreases with increasing cathode potential (or applied current density) in electrochemically deposited Fe-Cu [23], Co-Cu [24,25], and Co-Fe-Cu films [4].…”

“…Thin films of Fe, Co, and Ni and their alloys prepared using electrochemical deposition techniques have gained considerable interest owing to their potential applications in micro electromechanical system devices and data storage media [1][2][3]. Soft deposits based on Co-Fe are important materials and it has been reported that the addition of one or more elements including Ni and Cu into Co-Fe magnetic thin films can help to improve their specific properties [4][5][6]. However, few studies have been focused on ternary Co-Fe-Cu magnetic thin film systems electrochemically deposited under different experimental conditions.…”

“…Kalu et al studied the corrosion characteristics of Co-Fe-Cu films with and without phosphorus [6]. Mehrizi et al investigated the properties of Co-Fe-Cu deposits electrochemically deposited at various applied current densities [4]. In that study, the Co-Fe-Cu films containing up to 10 at.% of Cu content were observed to have optimum required properties [4].…”