Ni-Co Films Research Articles

Binary CoNi and Ternary FeCoNi Alloy Thin Films as High-Performance and Stable Electrocatalysts for Oxygen Evolution Reaction

Binary CoNi and Ternary FeCoNi Alloy Thin Films as High-Performance and Stable Electrocatalysts for Oxygen Evolution Reaction

Diffusion behavior and electrical performance of La2O3 doped Ni-Co films and their application as metallic interconnection of solid oxide fuel cell

The application of spinel coatings has been proposed to overcome the difficulties in ultilizing ferritic stainless steel as interconnection. In this paper, a La2O3-doped (Ni,Co)3O4 coating containing 15 wt% La2O3 was synthesized on a SUS430 stainless steel via codeposition, followed by thermal conversion of the deposited layer in air at 800 ℃ for 1000 h. The surface and cross-sectional microstructure of the samples is analyzed by scanning electron microscope, and X-ray diffraction. The results reveal that a tri-layer oxide structure with Co3O4 outer layer, (Ni,Co,Fe)3O4/(Ni,Co)3O4/(Ni,Co)O middle layer and (Mn,Cr)3O4/Cr2O3 inner layer is developed on the Ni-Co-La2O3 coated steel. This work is designed to elucidate the diffusion behavior of elements and the effect mechanism of the La2O3. The addition of La2O3 inhibits the growth of Cr2O3 at the coating/substrate interface. Moreover, a higher electrical conductivity has been achieved for the La2O3-doped coating sample.

Mechanical Stresses and Magnetic Properties of NiFe and CoNiFe Films Obtained by Electrochemical Deposition

Mechanical Stresses and Magnetic Properties of NiFe and CoNiFe Films Obtained by Electrochemical Deposition

Historical Perspectives on Evolution from Elctrodeposition to Electrochemistry

Among numerous findings by human beings, electrodeposition is of great importance in the whole invention and is getting to be a core technology to date. The applications of electroplating used in electronics devices, magnetic recording heads and media, chemical biosensors, and batteries are some typical examples surrounding our present world. Looking back on the history of electrodeposition, the first trial was carried out in the Mesopotamian-era in 1500 BC, which was a Sn plating on iron wares. For Japan, the beginning of plating was performed back in the 6th century for a Au amalgam plating on the Buddha statue at Asuka-era Temple. Hence, the technology of electrodeposition has been developed and evolved for a long period of time along with humankind.While electrodeposition is known to be a traditional way to form metal or non-metal ions on various substrates, it is still kept being one of the cutting edge technologies to date. Because desired thin films, such as CoFeNi for hard disk and Cu wiring for silicon devices, can be easily obtained by the fine control of the chemistry on the interface between the electrode and electrolyte. The sequential high-throughput with outstanding cost effectiveness also push forward this technology to practical applications in various industrial fields. An example of the fine control of deposited films popped up in our mind is the idea of UPD (underpotential deposition) by ad-atom in 1978. Such an idea of ppm or ppt content of metal ions in the plating bath resulted in the practical realization of electroless plating disk for PATTY HDD device (1981 NEC,NTT). Electrodeposition is also known to be a game-changer in the scientific history as well. For the fabrication of soft magnetic materials, the electrodeposited thin film of Co65Ni23Ni12 achieved low-Hc with high-Bs for the first time, which was breaking the common sense that high-Bs is incompatible with low-Hc in soft magnetic materials. [1, 2] Such an electroplating technology is on going to the next stage for 3D memories. Ever since electrodeposition was conducted in earnest by Jacobi et al in 1837, its practical use in sub-micron scale was established in 1997 as damascene process to ULSI internal wiring technology and is now available to handle atomic-scale of fabrication in various fields.This year marks the 100th anniversary of the establishment of the ECS Electrodeposition Division. There is no doubt that ECS has contributed significantly to the development of the Electrodeposition field since 1922. In today's lecture, we will introduce our research concept on electrodeposition in the various fields based on electrochemistry, such as magnetism, sensors, and electronics on the basis of our achievements of their practical use for future industrial usage including battery devices. [3][1] T. Osaka et al., “A soft magnetic CoNiFe film with high saturation magnetic flux density and low coercivity”, Nature, 392, 796 (1998).[2] T. Osaka et al., “Influence of crystalline structure and sulfur inclusion on corrosion properties of electrodeposited CoNiFe soft magnetic films”, Journal of the Electrochemical Society, 146, 2092 (1999).[3] T. Osaka, “Spotlight on Japanese Battery Technologies”, Nature jobs, 2015. Figure 1

(Invited) Chemistry Effects on the Electrodeposition of Re, Co, and Alloys

Electrodeposition has been adopted in various metallization processes. It allows conformal and super-conformal deposition on curved and recessed substrates, enables the fabrication of metals and alloys with well controlled composition, impurity, and grain structure, and provides fast growth rate, high throughput, and low cost of ownership. Organic additives have been used in electrolytes to tune not only the growth behavior, but also the impurity and grain structure of the deposited material. The most well-known cases are those used for magnetic alloy plating[1,2] in storage and MEMS industry and for damascene copper plating[3,4] in microelectronic industry. On the other hand, the electrolyte itself has largely remained aqueous for most cases. Organic solvents, room temperature ionic liquids, and deep eutectic systems have been widely studied with, however, relatively limited success in large scale adoption.The first part of this talk will introduce some studies on the electrodeposition of Cobalt as an alternative metal for semiconductor interconnect applications. Organic additives that tailor the deposition rate of cobalt are used to enable the Co filling in sub-micron structures. The effect of such additives on the impurity incorporation and film grain structure will be discussed. The second part of the talk will discuss some recent studies on the electrodeposition from “water-in-salt” electrolytes, where the hydration of a super high concentration of supporting salt depletes the free water molecules in the aqueous solution, thus limiting the hydrogen evolution reaction. The discussion will be in a context of Re and ReCo alloy deposition for superconducting connector applications for quantum devices. REFERENCES T. Osaka, M. Takai, K. Hayashi, K. Ohashi, M. Saito, and K. Yamada, A soft magnetic CoNiFe film with high saturation magnetic flux density and low coercivity, Nature, 1998, 392(6678), 796. E.I. Cooper, C. Bonhôte, J. Heidmann, Y. Hsu, P. Kern, J.W. Lam, M. Ramasubramanian, N. Robertson, L.T. Romankiw, and H. Xu, Recent developments in high-moment electroplated materials for recording heads, IBM Journal of Research and Development, 2005, 49(1), 103. P. Andricacos, C. Uzoh, J. Dukovic, J. Horkans, and H. Deligianni, Damascene copper electroplating for chip interconnections, IBM Journal of Research and Development, 1998, 42(5), 567. T.P. Moffat, J.E. Bonevich, W.H. Huber, A. Stanishevsky, D.R. Kelly, G.R. Stafford, and D. Josell, Superconformal Electrodeposition of Copper in 500–90 nm Features, Journal of The Electrochemical Society, 2000, 147, 4524.

Perpendicularly magnetized epitaxial Co/Ni multilayers grown on Ru(0001) layers by alternate monoatomic layer deposition

The hcp stacked Bh-ordered CoNi film was a candidate material to simultaneously have large uniaxial magnetic anisotropy energy (Ku) and a low Gilbert damping constant, which were previously predicted by a first-principles calculation. In this paper, we investigated the film growth condition to form the hcp stacked CoNi layers. [Co(1 ML)/Ni(1 ML)]N multilayers were epitaxially grown on Al2O3(11-20)/Ru(0001) underlayers by molecular beam epitaxy using an alternate monoatomic layer deposition technique with changing growth temperature (Ts) and repetition number (N). As the results of structural characterizations by x-ray diffraction measurements, it was found that the fcc- and hcp-CoNi phases were mixed in the samples, and the volume fraction of the fcc phase was larger than that of the hcp phase. However, the formation of the hcp-CoNi phase was promoted near the interface with the Ru layer having the hcp structure. The low growth temperature and the small N increased the volume fraction of the hcp phase. The Ku value of 5.1 Merg/cm3 was achieved for the [Co(1 ML)/Ni(1 ML)]20 multilayer grown at room temperature. In addition, a perpendicularly magnetized film was realized even for the thin sample with N = 5 (2 nm). This means that the Co/Ni multilayers are a thin ferromagnetic material suitable for application to spintronic devices.

Investigation of Structural and Magnetic Properties of Co, Ni and CoNi Alloy Thin Films by Fabricated with Electrodeposition

The production of nanoparticles as thin film coating performed with electrodeposition method is easier and cheaper than other methods. Because, thin film production can be controlled with the change of ingredients in the bath composition. In this study, Co, Ni, and CoNi alloy thin films were fabricated with electrodeposition method through the bath composition that consists of cobalt sulphate (CoSO4.7H2O), nickel sulphate (NiSO4.6H2O), nickel (II) chloride (NiCl2 6H2O) and boric acid (H3BO3). Crystal structure (XRD), morphological (SEM), elemental composition (ICP) and magnetic properties (VSM) of the fabricated thin films were investigated. Chemical properties of coating bath (CV) was examined as well. Magnetization measurements of the thin films were performed by applying magnetic fields between + 75000 Oe and -75000 Oe and then hysteresis loops were obtained. The Co, Ni, and CoNi films showed ferromagnetic material properties. Coercivity (Hc), permanent magnetization (Mr), saturation magnetization (Ms) values of these alloys were significantly affected by the amount of the cobalt, magneto crystal anisotropy and grain size. It was understood that some materials having hard and soft magnetic properties can be fabricated by controlling the bath composition.

Microstructure and corrosion resistance of highly oriented electrodeposited CoNiFe medium-entropy alloy films

The medium-entropy alloy is a newly intriguing material showing superb properties. A simple, one-step method was developed to electrodeposit CoNiFe medium-entropy alloy films from a sulfate and citrate bath. The microstructure and corrosion resistance were investigated in CoNiFe films with varying deposition current densities. It shows the face-centered cubic structure with a <111> preferential orientation. HRTEM-EDS observations further show information on the nanostructure and element distribution. The films exhibit a strong corrosion resistance in 3.5 wt.% NaCl solution. The films electrodeposited with a current density of 44.4 A/dm2 shows a low self-corrosion current density of 4.72 × 10−6 A⋅cm−2 in 3.5 wt.% NaCl solution. The corrosion mechanism was proposed in combination with electrochemical impedance spectroscopy results. The outstanding properties were attributed to the near-equimolar ternary components. The results lay a solid foundation for developing of highly oriented medium-entropy alloy films with strong corrosion resistance.

Features of the Electrochemical Deposition of Films from a Triple System of CoNiFe

The nature of phenomena that occurs in the electrolyte during the electrochemical deposition of CoNiFe films and the mechanism leading to the difference in the relative content of elements in the electrolyte and film was clarified. This clarification was obtained with the help of a spectrophotometric study of chloride electrolytes and the electrochemical deposition of CoNiFe films at 70 °C. An experimental study of the absorption spectra and the pH values of the FeCl2, NiCl2 and CoCl2 salt solutions at concentrations of 0.005 to 1 mol/l showed the complex nature of the ion-formation balance in single-component and mixed solutions and the dependence of ion formation on acidic and alkaline additives. The deposited CoNiFe film was made from a chloride electrolyte with a component content ratio of 1:1:1 at both high (0.5 mol/l) and low (0.006 mol\l) concentrations of each component. The content of each component in the film after the electrochemical deposition of the three component solution (FeCl2, CoCl2, and NiCl2 at equal concentrations) did not correspond to the composition of the electrolyte. The mechanism for the abnormal deposition of Co, Fe, Ni occurred due to the incomplete ionization of atoms and the differences in the mobility of ions. The magnetic susceptibility of the films formed in the triple CoNiFe system was higher than that of a permalloy. Therefore, the triple system shows promise for use in magnetic field converters.

Features of the Electrochemical Deposition of Films from a Triple System of CoNiFe

The nature of phenomena that occurs in the electrolyte during the electrochemical deposition of CoNiFe films and the mechanism leading to the difference in the relative content of elements in the electrolyte and film was clarified. This clarification was obtained with the help of a spectrophotometric study of chloride electrolytes and the electrochemical deposition of CoNiFe films at 70 °C. An experimental study of the absorption spectra and the pH values of the FeCl2, NiCl2 and CoCl2 salt solutions at concentrations of 0.005 to 1 mol/l showed the complex nature of the ion-formation balance in single-component and mixed solutions and the dependence of ion formation on acidic and alkaline additives. The deposited CoNiFe film was made from a chloride electrolyte with a component content ratio of 1:1:1 at both high (0.5 mol/l) and low (0.006 mol\l) concentrations of each component. The content of each component in the film after the electrochemical deposition of the three component solution (FeCl2, CoCl2, and NiCl2 at equal concentrations) did not correspond to the composition of the electrolyte. The mechanism for the abnormal deposition of Co, Fe, Ni occurred due to the incomplete ionization of atoms and the differences in the mobility of ions. The magnetic susceptibility of the films formed in the triple CoNiFe system was higher than that of a permalloy. Therefore, the triple system shows promise for use in magnetic field converters.

Electrodeposited Ni-Co Films from Electrolytes with Different Co Contents

Ni–Co alloy coatings were electrodeposited at various cobalt amounts on pretreated steel substrates. The co-deposition phenomenon of Ni-Co alloys was described as anomalous behaviour. Different techniques including scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX), X-ray diffraction (XRD) and potentiodynamic polarization were used to characterize the alloy coatings. EDX results showed that the Co content increase with the enhancing of Co amount. SEM images have shown that the increase of Co amount leads grain developing from large grain to branched grain form and that goes through spherical and pyramidal, this implies that the grain size of these alloy coatings is greatly affected by Co amount in the electrolyte baths. XRD patterns revealed that the phase structure of Ni–Co coatings is dramatically changed from fcc into hcp structure with the increase of Co amount. The electrochemical properties of Ni-Co alloy coatings evaluated in 3.5% NaCl solution reveal that Ni–34.32 wt.% Co alloy exhibits better corrosion resistance compared to pure Ni and other Ni–Co alloy coatings.

Формирование пленок тройной системы CoNiFe электрохимическим осаждением

High-permeability films of CoNiFe triple system form the basis for high-density magnetic data storage. Electrochemical deposition of CoNiFe films, as contrasted with «dry» processes, gives more homogeneous coating with lesser defect level and allows reinforcing the films thickness without stresses. This study investigates the nature of the phenomena taking place at electrochemical deposition of CoNiFe films and leading to the difference in the relative content of the elements in the electrolyte and in the film. The hydrogen exponent of chloride electrolytes was examined in the temperature range of 25–70 °C and electrochemical deposition of CoNiFe films at 70 °C was studied. It was demonstrated that CoCl2, NiCl2, FeCl2 salt solutions with concentration from 0,006 to 1 mole/l are characterized by complex process of ion balance formation in single and mixed solutions. The deposition of CoNiFe films was carried out from chloride electrolyte with a component content ratio of 1:1:1 at an average concentration of 0,083 mole/l of each component. It has been established that the content of the component in the film at electrochemical deposition of three-component solution CoCl2, NiCl2, FeCl2 with equal concentration of each component did not correspond to the composition of the electrolyte but was closest to the composition of the electrolyte at a decrease in the concentration of each component at high current density.

Relationship between Current Density, Crystal Grain Size, Composition and Mechanical Properties in Electrodeposited Ni-Co Alloys

Nickel [1], cobalt [2], and their alloys have been investigated as important engineering materials because of their unique properties, such as magnetic, heat-conductive and high hardness. Much interest is focused on the application of Ni-Co alloy films in micro-electrical-mechanical systems (MEMS) devices especially their considerable potential in manufacturing of magnetic actuator due to excellent electrical and mechanical properties [3].Reliability of electronic components is highly dependent on the mechanical property, which is closely related to its average grain size according to grain boundary strengthening mechanism [4]. Nanocrystalline materials can offer enhanced mechanical strength compared with coarse-grained counterparts when device components are scaled to the micro-scale regime with synergistic effect of the sample size effect [5]. Meanwhile, alloying allows utilization of the solid solution strengthening mechanism to further enhance the mechanical strength [6], and Ni-Co forms a solid solution over the whole concentration range, making it easy to control the mechanical and magnetic properties.Electroplating is a promising technique in controlling crystalline properties of Ni-Co alloy films because the morphology, composition, grain size, and deposition rate of the deposited materials can be facilely controlled by varying the electroplating parameters, such as the current density, bath composition, and temperature [7]. Therefore, in this study, the effects of applied current density on average grain size, composition, and micro-mechanical properties of electrodeposited Ni-Co films are evaluated for fabrication of micro-components in electronic devices. The electroplating was carried out at 55 ℃, and the current density was varied from 5 to 20 mA/cm2. A piece of Pt plate was used as the anode. Crystalline structure of the Ni-Co films was characterized by X-ray diffraction (XRD), average grain size was determined using XRD in conjunction with the Scherrer method. Microhardness tests were conducted on a Vicker's hardness tester using a load of 0.025 kg, applied for 15 s. Composition was analysed by energy dispersive X-ray spectroscopy (EDX) system. Furthermore, alloy films are processed into micro-pillars in a size of 10×10×20 μm3with focused ion beam (FIB, FB2100, Hitachi) milling. The optical microscope photograph of Ni-Co alloy micro-pillar fabricated with current density of 18 mA/cm2 is shown in Fig. 1. A high yield stress of 1.65 GPa is determined after the micro-compression test.Vickers hardness as a function of d -1/2 for the alloy specimens is shown in the scatter plot of Fig. 2, where d is average grain size. Microhardness value has a positive linear relationship with d -1/2 approximately, which corresponds well to Hall-Petch relationship. Maximum Vicker's hardness value of 526 Hv was obtained with a current density of 10 mA/cm2, which is much higher than those of pure Ni (306 Hv) and Co (403 Hv) films prepared in this study, indicating the effect of solid solution strengthening.[1] T. Yamamoto, K. Igawa, H.C. Tang, C.Y. Chen, T.F.M. Chang, T. Nagoshi, O. Kudo, R. Maeda, M. Sone, Microelectron. Eng. , 213, 18 (2019).[2] X. Luo, C.Y. Chen, T.F.M. Chang, H. Hosoda, M. Sone, J. Electrochem. Soc. , 162, D423 (2015).[3] M. Duch, J. Esteve, E. Gómez, R. Pérez-Castillejos, E. Vallés, J. Micromech. Microeng. , 12, 400 (2002).[4] C.Y. Chen, M. Yoshiba, T. Nagoshi, T.F.M. Chang, D. Yamane, K. Machida, K. Masu, M. Sone, Electrochem. Commun. , 67, 51 (2016).[5] M. D. Uchic, D. M. Dimiduk, J. N. Florando, W. D. Nix, Sc ience , 305, 986 (2004).[6] H. Tang, T.F.M. Chang, Y.W. Chai, C.Y. Chen, T. Nagoshi, D. Yamane, H. Ito, K. Machida, K. Masu, M. Sone, J. Electrochem. Soc. , 165, D58 (2018).[7] A. Bai, C.C. Hu, Electrochimica Acta , 47, 3447 (2002). Figure 1

Electrochemical Deposition of CoNiFe Alloy from Concentrated Chloride Electrolyte

Heating the chloride electrolyte to a temperature of 70 °C at the concentration ratio of CCo:CNi:CFe 1:1:1 provides stabilization of electrochemical deposition of the CoNiFe alloy components as a result of discharge of metal ions (Fe2+ Cl- )+ , (Со2+ Cl- )+ , (Ni2+ Cl- )+. Electrolyte filtering and correcting pH with HCl provides a reproducible deposition of CoNiFe films. Based on the experimental results of the CoNiFe films, a mechanism of electrochemical deposition is proposed, which differs in view of the phenomena occurring in the volume of electrolyte: mass draft ions, with the determining effect of mobility and the formation of positive ions on the anode. CoNiFe films are produced without mechanical stresses, with a uniform structure and with high magnetic parameters without high heat firing.

Mechanism of the Electrochemical Deposition of a CoNiFe Alloy

Heating the chloride electrolyte to a temperature of 70°C ensures the normal codeposition of the components of the CoNiFe alloy as a result of the discharge of single-charged iron and cobalt species (Fe2+Cl-)+ and (Co2+Cl-)+, respectively and double-charged Ni2+ ions at a high cathode current density. The chloride electrolyte obtained with filtration and pH correction by hydrochloric acid provides the electrochemical deposition of CoNiFe films with a CCo:CNi:CFe ratio of 1:1:1. The mechanism of the abnormal deposition of Co, Fe and Ni occurs due to the incomplete ionization of atoms and differences in ion mobility. Based on the experimental results of CoNiFe films, an electrochemical deposition mechanism is proposed. In contrast to the well-known in the literature, the phenomena occurring in the volume of electrolyte, including transmission of ions, with the determining effect is the mobility and formation of positive ions on the anode. CoNiFe films are produced without mechanical stresses, with a uniform structure and with high magnetic parameters without a high burn temperature. Electrochemical deposition when the charge of ions in the electrolyte is taken into account allows to obtaining a reproducible electrochemical deposition of CoNiFe films.

Structure and magneticproperties of barium hexaferrite BaFe10CoNiO19 films

We prepared Co-Ni doped BaFe10CoNiO19 films on the quartz glass substrates by ultrasonic spray pyrolysis with different molarities. The precursor was prepared by dissolving barium nitrate (Ba(NO3)2), iron nitrate (Fe(NO3)3.9H2O), cobalt nitrate (Co(NO3)2.6H2O), nickel sulfate (Ni2SO4.7H2O) in 50 mL of distilled water. Precursor solution was sprayed onto the cleaned quartz plates previously heated to 150 – 200°C, using a sprayer and argon as carrier gas. For crystallization the films were annealed in a furnace at a temperature 1000°C for3 hour in atmosphere ambient. By scanning electron microscopy (SEM), the barium hexaferrite BaFe10CoNiO19 films shows agglomeration and the average diameter of particles less than1 μm. We believed, the structure of barium hexaferrite BaFe10CoNiO19 films change due to Co-Ni existence. Therefore, the magnetic properties deteriorate by incorporation of Co-Ni into the structure of barium hexaferrite BaFe10CoNiO19.

Template-Assisted Co-Ni Nanowire Arrays.

A comparison was performed between Co-Ni thin films and template-assisted nanowires arrays obtained by electrochemical co-deposition. To reduce the effects of anomalous deposition and increase the Ni content in the deposit, an electrolyte with three times more Ni than Co in atomic ratio was chosen. Electrochemical deposition was performed at constant potentials chosen in the range from E = −0.8 to −1.2 V vs. Ag/AgCl. Cyclic voltammetry, chronoamperometry, and charge stripping techniques were used to characterize and compare the electrochemical behavior of Co-Ni films and nanowires. Morphological and compositional characterization was performed by scanning electron microscopy (SEM/EDAX) to assess the influence of the deposition potential on the growth of film and nanowires. A comprehensive analysis of the deposit growth rates for thin films and nanowires is presented taking into consideration the hydrogen evolution and anomalous deposition. The comparative study of the composition of film and nanowires obtained at different deposition potentials has shown that deposition of nanowires with a film-like composition takes place at more positive potential than thin film.

Study on the changes of ultrasonic parameters over supercritical Ni-Co electroplating process

This work discusses the influence of changes to ultrasound (US) parameters over the nickel cobalt (Ni-Co) metal thin film properties produced by supercritical CO2 (SC-CO2) electroplating. Additionally, Ni-Co films were produced by conventional electroplating and silent SC-CO2 and compared against each other. The discussion on metal thin film properties revolves around variations to the bath type ultrasonic power (15 W and 20 W) and frequency (42 k Hz and 72 kHz) during experiments. The properties provided by the three electroplating processes and analyzed include: grain sizes, film elemental content analyses, surface microstructures, film hardness, corrosion resistance, surface roughness, crystalline structure and preferential growth, etc. From the results it was clear that quality of films produced by US-SC-CO2 was improved compared to that of films produced by silent SC-CO2, which itself was better than those produced by conventional electroplating. However, when US power was varied we observed a decline in the mechanical properties of the produced films. The combination of ultrasonic agitation with SC-CO2 allows for improved mechanical properties such as: lower surface roughness, finer grain size and surface morphologies, increased corrosion resistance and film hardness. The ultrasound agitation applied to SC-CO2 electroplating enhanced the formation of alloyed metal as ultrasonic agitation increased the electrolyte flowability during electroplating process resulting in increased mass transfer while at the same time achieving a surface cleaning effect which removed metal ions with poor adhesion and other unwanted particles. Moreover, application of ultrasonic agitation avoids the use of surfactants so only changes to the physical phenomena and no changes to the chemical composition of the deposited thin films were observed, meaning less pollution to the electrolyte and higher purity of the deposited films. The US-SC-CO2 electroplating method described in this work effectively enhanced the mechanical properties of the deposited thin films compared to those produced by both silent SC-CO2 and conventional electroplating processes.

Effect of Co-deposited αCo(HCP) and βCo(FCC) on magnetic property of Co-Ni soft magnet film prepared by Pulsed Electrodeposition

The αCo (Hexagonal close packed structure, HCP) and βCo (Face centred cubic structure, FCC stable after 417°C) co-exists in Co-Ni magnetic alloy film deposited over stainless steel substrate, by galvanostaticpulsed electrodeposition method. FEG-SEM images reveal Polyhedral crystallite over sample surface exposed to the electrolyte. X-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) study confirm Co-Ni alloy formation at room temperature. XRD patterns confirm the co-existence of FCC (110) Co, HCP (220) Co and FCC (220) Ni, which in turn reproduced in anisotropic nature of magnetic curve Parallel and Perpendicular to the applied magnetic field. Differential Scanning Calorimetric (DSC) shows that high concentration Co88Ni12 alloy film is thermally stable up to 450°C.

Study on Anomalous Codeposition Phenomenon of CoNi Magnetic Films

CoNi alloy films prepared from electrolytes with various concentrations of cobalt ions were studied in the paper. Influences of different cobalt ions concentrations on electrochemistry processes, components, microstructures, surface morphologies and magnetic properties of CoNi films were investigated. It was found that CoNi film plating was a kind of anomalous codeposition process. The percentage of cobalt content in CoNi films was higher than that of in the electrolyte. Moreover, with the rise of cobalt ions concentrations, the percentage of cobalt content in the samples increased gradually. CoNi films possessed crystal structures with four stronger diffraction peaks. However, CoNi films prepared from bath with higher cobalt ions possessed hcp structures which contributed to dendrite structures resulting in the increase of coercivity.