Development of electroplated magnetic materials for MEMS

Electrodeposition of FeCoNi thin films for magnetic-MEMS devices

The effect of magnetic fields on the electrodeposition of CoFe alloys

We investigated the electrochemical deposition process of Fe-Co-Ni alloys from sulfate electrolytes containing no organic additives and the structural, magnetic, and electrical properties of the resulting films. The effect of pH and Co and Fe concentrations in the electrolyte on alloy composition is examined. The pH of the solutions is kept at 2.8 to minimize the incorporation of nonmagnetic matter. With increasing Ni content, a transition of the film structure from body-centered cubic (bcc) to face-centered cubic (fcc) is observed. X-ray diffraction and transmission electron microscopy results show that the smallest grain size of about 10 nm is obtained when the bcc and fcc phases coexist. Films with biphasic structure exhibit soft magnetic properties (coercivity about 1 Oe), high magnetic moment (about 2.1 T), narrow dispersion of the easy axis (less than 3°), and good high frequency response, with a resonance frequency above 1.8 GHz. Stress anisotropy has an important role in determining soft magnetic properties. © 2003 The Electrochemical Society. All rights reserved.

https://iopscience.iop.org/article/10.1149/1.1545462/pdf

Structural and Magnetic Characterization of Electrodeposited, High Moment FeCoNi Films

Enhancement of current for solutions, containing Ni +2 , Fe +2 , and H + ions, has been observed by linear sweep voltammetry and chronoamperometry when a magnetic field of 0.1 T was applied parallel to the cathode. The current enhancement in a magnetic field was attributed to the convection near the electrode surface induced by the Lorentz force. There is a decrease of the Fe content in NiFe films by approximately 4% obtained with applied magnetic field. It was also demonstrated that the applied magnetic field affects the magnetic properties, crystalline structure and/or texture, stress, and surface roughness of NiFe films.

Effect of Magnetic Field on Electrode Reactions and Properties of Electrodeposited NiFe Films

The properties of soft magnetic CoNiFe films electrodeposited in the presence of saccharin and sodium lauryl sulfate additives were studied in terms of their thickness and substrate dependence. Auger depth profile analysis of the elemental composition in CoNife films electrodeposited over different substrates (Pd 00 Ni 10. 1.0 T NiFe.Cu) demonstrate that the average composition at the substrate interface and bulk deposited films remains constant. X-ray diffraction (XRD) measurements reveal the existence of mixed fcc + bcc phase with larger amounts of bcc crystallites near the substrate side of the films, i.e.,at the lower thickness. XRD and transmission electron microscopy measurements revealed a larger grain size at the CoNiFe/substrate interface. The measured average stress is both substrate- and thickness-dependent. The easy-axis coercivity, H c , follows the Neel's relation H c = ct n (t is the thickness and c is a constant). It was found that the value of the exponent n is substrate dependent. Mechanisms related to the coercivity of CoNiFe films deposited ovar different substrates (1.0 T NiFe, Cu, Pd 90 Ni 10 , high magnetic moment CoNiFe) are discussed in terms of material properties of these magnetic films.

Venkatesewara Inturi

Papers

Composition, Structure, Stress, and Coercivity of Electrodeposited Soft Magnetic CoNiFe Films: Thickness and Substrate Dependence

Composition, Structure, Stress, and Coercivity of Electrodeposited Soft Magnetic CoNiFe Films — Thickness and Substrate Dependence.