Venkateswara Rao Inturi

Organic Additives in the Electrochemical Preparation of Soft Magnetic CoNiFe Films

Electrochemical preparation of CoNiFe films was investigated from the viewpoint that the organic additives present in the plating bath are one of the most important factors in obtaining soft magnetic materials. Soft CoNiFe films with Bs 5 1.2 to 2.0 T were obtained by plating in the presence of different additives. The results demonstrated a strong influence of different additives present in the electrolyte on current efficiency, electrode kinetics, alloy composition, anomalous order of codeposition, corrosion resistivity, saturation magnetic flux density, coercivity, and stress in CoNiFe films.

High saturation magnetization films of FeCoCr

Thin (∼1000 A) films of (Fe54Co46)1−xCrx have been prepared by magnetron sputtering on Si/SiO2 substrates. The films were shown to be body-centered-cubic and (110) textured. It was found that the Fe54Co46 films possess a saturation magnetization of 24.5 kG at room temperature. Doping the Fe54Co46 films with Cr in the range of 0–13 at. % increased corrosion resistance, electrical resistivity, and reduced the saturation magnetization as a function of the amount of added Cr. The coercivity of both doped and undoped as-deposited films (80–120 Oe) decreased substantially after a 220 °C magnetic anneal. Electrochemical corrosion testing was done in two chloride salt solutions. Potentiodynamic scans performed on films in a 0.47 M chloride bath solution at pH=2.9 showed a substantial increase in corrosion resistance of the films between 6.6 and 8.2 a/o Cr. Similar scans performed in a 0.01 M chloride solution at pH=5.8 showed good corrosion resistance for all the films.

Practical FeCo Films for Perpendicular Writer Pole

An attempt is made in this publication to review various developments of FeCo films for recording heads in the last decade and to look at emerging developments regarding these films. A series of FeCo films from 100% Fe to 100% Co was sputter deposited, characterized, and analyzed for various magnetic properties such as magnetostriction, uniaxial anisotropy, coercivity, dispersion, and saturation magnetization. Many process parameters, with the most influencing parameter being sputter pressure, play an important role especially influencing dispersion and/or hard axis coercivity (Hch) in these materials. Out of the many developments to date the effect of seed layer(s) in reducing grain size of high moment bcc FeCo films is still intriguing and, hence, a comprehensive review and analysis of seed layer effects are included. Although film stress can play an important role in optimizing Hch, there is no clear trend seen between film stress and Hch when viewed across broad processing conditions. Higher Hk evolution with oblique deposition is an interesting phenomenon in these films. Uniaxial anisotropies of nearly 1000 Oe were found. The anisotropy evolution is explained through magnetoelastic energy and through crystal structure. Even though these films are very columnar in nature it was found that there was little to no fiber texture present in these films and there was no difference in texture between fine grained and coarse grained FeCo films.

Within wafer magnetic anisotropy in sputtered FeCo films

Seeded FeCo films were studied as a function of aligning field, thickness, deposition power density, and pressure. Magnetic and nonmagnetic parameters were investigated with an emphasis on within wafer magnetic dispersion, which was measured using both a magnetic loop tracer and a magneto-optical Kerr effect mapper. Magnetic dispersion changes significantly with all variables studied, although correlations between other magnetic parameters, resistivity, and stress are not consistently observed.

Magnetic Anisotropy Dispersion in FeCo Films

We report on our study of magnetic and nonmagnetic parameters such as coercivity, anisotropy , magnetic dispersion, and stress on FeCo films of various thicknesses from 25 A to 500 A . We used 10 A Ru or NiFe seed layers for two sets of FeCo films. All films showed so-called hard-axis coercivity rocking, i.e., the hard-axis coercivity exhibits two local minima close to the nominal hard axis. Magnetic properties and stress change dramatically with FeCo thickness, but with little difference between the two types of seed materials. We found a correlation between the angular separation of the two local coercivity minima and easy-axis coercivity. The results stress the need to differentiate between two levels of dispersion, one at the microscopic and the other at the macroscopic level.

Volume exchange in soft FeCo films of high magnetization

Soft FeCo films of high magnetization are a well known integral part of today’s magnetic recording heads. Values for the volume exchange, an important parameter since it determines exchange length, domain wall width, and energy are, however, available for few compositions of FeCo in spite of the widespread use of these alloys. This paper presents results for volume exchange on Fe65Co35 determined by means of a detailed Brillouin light scattering study, one of a few methods that permit the measurement of exchange. A set of Fe65Co35 films of various thickness values was examined, and volume exchange was found to be 3.5 × 10–6 erg/cm, far higher than what is often assumed.