Ibro Tabakovic

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

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 Neels 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.

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

Mechanism of Saccharin Transformation to Metal Sulfides and Effect of Inclusions on Corrosion Susceptibility of Electroplated CoFe Magnetic Films

The electroplated magnetic alloys 1.0T Ni80Fe20, 1.6T Ni45Fe55, 2.4T Co40Fe60, obtained in the presence of saccharin, and sputtered magnetic alloys of the same composition showed dramatically different corrosion properties at pH 5.9. The higher corrosion susceptibility of electroplated magnetic alloys, known for many years, was generally attributed to sulfur inclusions into the deposit. However, there was no direct evidence of the structure of sulfur-containing molecules included in deposit. We have analyzed electroplated, EP-CoFe, and sputtered, SP-CoFe, magnetic films using electrochemical, secondary ion mass spectroscopy, X-ray photoelectron spectroscopy XPS, and high-pressure liquid chromatography HPLC techniques. The analysis of electroplated CoFe films obtained in the presence of saccharin revealed saccharin, benzamide, o-toluenbenzamide HPLC and metal sulfides XPS in EP-CoFe deposit. The proposed mechanism for saccharin transformation to metal sulfides involves four steps: i a reductive cleavage of C-S bond in saccharin giving rise to benzamido sulfinate, ii a desulfurization step leading to benzamide and sulfur dioxide, iii an electrochemical reduction of sulfur dioxide to hydrogen sulfide, and iv a reaction between H2 Sa nd M +2

Influence of Solution pH and Concentration of Saccharin on Electrodeposition and Properties of 2.4 T CoFe Alloys

Electrodeposition of 0.5 μm thick 2.4 T CoFe films with 60-63 wt % Fe was achieved at various solution pH values (2.0, 2.2, 2.3, 2.4, 2.6, and 2.8) in the presence of saccharin on 6 in. AlTiC wafers with a Cu seed layer. The effect of pH on the electrodeposition including voltammetric behavior, plating rate, and selectivity ratio was discussed. The increase in the solution pH affected some material properties such as surface roughness, grain size, morphology, and corrosion. The texture, coercivity, and tensile stress of the 0.5 μm 2.4 T CoFe films with 60-63 wt % Fe were less affected by the solution pH. Possible reasons for such behavior were discussed. The increase in saccharin concentration from 0.1 to 2.0 g/L did not affect the roughness and corrosion of the electrodeposited 2.4 T CoFe films at pH 2.0 but had an influence on their composition, stress, and coercivity.

Effect of Magnetic Field on NiCu Electrodeposition from Citrate Plating Solution and Characterization of Deposit

The effect of an external in-plane magnetic field (B = 0.1 T) on the electrodeposition of NiCu films from a citrate bath solution was studied. The application of the magnetic field showed the following effects: (i) an increase of limiting current for Cu 2 + reduction, (ii) an increase of plating rate of NiCu by ∼17%, (iii) an increase of Cu content in NiCu deposit of 4.9%, (iv) a decrease of tensile stress on NiCu films, (v) a strong influence on the texture, and (vi) a strong influence on surface morphology resulting in three-dimensional (3D) growth without applied magnetic field and 2D growth with applied magnetic field.

High Magnetic Saturation Poles for Advanced Perpendicular Writers

Advanced perpendicular writers continue to demand maximum write fields, fast rise times at ever vanishing head-media spacing and strict reliability standards. This means that the asymptotic progression to a 2.4 T pole with nearly ideal magnetic response continues. At the same time we must control critical pole dimensions, fabricate at a reasonable cost while protecting against corrosion and erasure risks. We will review progress made to meet this challenge in a discussion of high moment materials utilizing electroplating and sputter deposition for single layer films and laminates. Concerns for corrosion will be assessed and minimized by controls on key contaminants. Micromagnetic modeling will be used to study the phenomenology and expected performance impacts of these various materials and structures. Results will be used to provide a better insight into the potential materials/design tradeoffs that must be made. In conclusion, performance and reliability will be assessed through electrical testing.