Tailoring the Morphology, Structure and Magnetic Properties of Electrodeposited CoFe Films onto Si(100) by In-Situ Uniform and Gradient High Magnetic Fields

Abstract

In this work uniform high magnetic field of up to 12 tesla and well-defined magnetic field gradients were in-situ applied during the electrodeposition process of CoFe alloy films on Si(100) substrate with Ni seed-layer. The evolution of morphology obtained by LSCM and AFM revealed that the electrodeposition under uniform or gradient magnetic fields provides advantage of forming high quality films with small grains size and low surface roughness. The X-ray diffraction measurements revealed that the crystalline structure of the films changed with the increase of magnetic flux density from face-centered cubic (fcc) at 0 T to body-centered cubic (bcc) at 12 T. However, the formation of a mixture phase (fcc+bcc) under gradient magnetic fields reflected a negative effect of the field gradient force on the transformation from fcc phase to bcc phase. With increasing magnetic flux density (B), the saturation magnetization (Ms) and coercive force (Hc) of the films increased, while in the case of B = 12 T, both of Ms and Hc decreased. It could be ascribed to the changes in the chemical composition and the formation of the mixture phases, due to the combined effects of the paramagnetic force, micro-MHD and the field gradient force under different magnetic field conditions. Soft magnetic films have been widely used in the fields of magnetic recordings, magnetic sensors and micro-electromechanical system (MEMS). 1-2 As a kind of typical soft magnetic materials, CoFe alloy films exhibit the highest saturation magnetization of 2.45 T and lower coercivity of about 2 Oe. 1 The magnetic properties of CoFe films depend on their morphology, crystal structure and composition. Although there are many methods available for the preparation of CoFe films, such as sputtering, molecular beam epitaxy, ion beam deposition and so on, 3-5 electrodeposition shows low cost, high efficiency and no size or shape limit for the preparation of nano-scale films.However, it's not easy to control the growth and morphology of CoFe films accurately in the complex circumstances. The morphology and microstructure, which largely affect the magnetic properties of CoFe films, are often determined by the deposition conditions such as the pH value, 6 deposition potential, 7 addition agents 8 and so on. Moreover, the addition of the sulfur and boron containing surfactants was verified to contaminate the CoFe films, damaging the magnetic performance. 9 In recent years, magnetoelectrodeposition, 10 as an emerging interdisciplinary field, has received broad attention from a number of research groups. 11 It is known that magnetic field has remarkable influences on the movement of electroactive species, increasing the limiting current density 12 and causing the changes of the morphology 13-15 and composition 16 of the deposited films. The major effects of magnetic field on the electrodeposition process can be explained with magnetohydrodynamic (MHD) effect induced by Lorentz force ( F L = j × B, where j is thr current density in A m −2 , B is the applied field in tesla...

Homogenizing of Pt on NiCu films for enhanced HER activity by two-step magneto-electrodeposition

“…21 The external magnetic field could improve the dispersion rate of NiCu particles on the cathode surface and increase the active specific surface area. 22 In a previous work, 23 we successfully prepared fine and CoFe particles uniformly deposited on Si (100) substrates containing Ni sub-crystal layers using a uniform gradient magnetic field assisted electrodeposition method. It was noted that the applied magnetic field strength was too high during the electrodeposition process, and therefore, the deposit tended to form dendritic crystalline structures.…”

Electrodeposition of Composite Ni-TiO2 Coatings from Aqueous Acetate Baths

“…Modification of the magnetic field configuration may influence the composition, structure and morphology of alloys and semiconductors. [10,[27][28][29][30] Lorentz force acts on ions as well as diamagnetic particles moving in the electromagnetic field if the lines of electric field crossing magnetic field ones. Interaction between disturbed electric field and magnetic field result in generation of Lorentz force which in turn is responsible for magnetohydrodynamic effect (MHD).…”

Archives of Metallurgy and Materials

“…The magnetic field may be an additional factor influencing the kinetics of electrode processes and simultaneously the properties of synthesized materials. Literature reports show possibilities of the application of a magnetic field of parallel orientation of the magnetic field induction vector versus the working electrode surface towards the modification of the composition, structure and morphology of alloys and semiconductors [14][15][16][17][18]. The Lorentz force acts on ions as well as diamagnetic particles moving in the electromagnetic field if the lines of the electric field cross the magnetic field ones.…”