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We have used molecular-beam epitaxy to grow high-quality pseudomorphic Ni and Co1Ni9 films on Cu(001). From temperature-dependent surface magneto-optic Kerr effect measurements of these films, we have determined the finite-size scaling behavior of the Curie temperature of ultrathin films for a thickness range of n=2.5–16 monolayers (ML). The film thickness dependent Curie temperature for each of these ferromagnetic thin-film systems, TC(n), is described by a finite-size scaling formula: [TC(∞) − TC(n)]/TC(n) = [(n − n′)/n0]−1/ν, where TC(∞) is the bulk Curie temperature, n0=2.5±0.5 ML for Co films and 3.5±0.4 ML for Ni and Co1Ni9 films is the microscopic length scale, and ν=0.76±0.08 is the bulk correlation length exponent. An interesting result is that TC(n) extrapolates to zero in the single mononolayer limit, n′=1.

The electroplated magnetic alloys ͑1.0T Ni 80 Fe 20 , 1.6T Ni 45 Fe 55 , 2.4T Co 40 Fe 60 ͒, 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 ͑XPS͒, and high-pressure liquid chromatography ͑HPLC͒ techniques. The analysis of electroplated CoFe films obtained in the presence of saccharin revealed saccharin, benzamide, o-toluenbenzamide ͑HPLC͒ and metal sulfides ͑XPS͒ in EP-CoFe deposit. The proposed mechanism for saccharin transformation to metal sulfides involves four steps: ͑i͒ a reductive cleavage of C-S bond in saccharin giving rise to benzamido sulfinate, ͑ii͒ a desulfurization step leading to benzamide and sulfur dioxide, ͑iii͒ an electrochemical reduction of sulfur dioxide to hydrogen sulfide, and ͑iv͒ a reaction between H 2 S and M +2 ͑M = CO, Fe͒ to metal sulfides. The higher corrosion susceptibility of EP-CoFe magnetic alloys than SP-CoFe magnetic alloys is discussed in terms of the mechanism of sulfur-assisted corrosion.Saccharin is an additive that has been widely used for more than three decades in the industry for electrodeposition of magnetic alloys such as 1.0T NiFe, 1 1.6T NiFe, 2 and 1.8T CoNiFe, 3-5 used as writer materials in the recording heads. It has been reported that saccharin reduces tensile stress, 1,6 grain size, 6 roughness, 7 and coercivity 1-6 of magnetic materials. However, it is also known that electroplated magnetic films in the presence of saccharin show higher corrosion susceptibility than magnetic films deposited without saccharin or sputtered by vacuum deposition. [8][9][10][11] The higher corrosion susceptibility of electroplated magnetic alloys was generally attributed to sulfur inclusions into the deposit. Notably, the sulfur in the deposit was associated with saccharin present in the plating bath but there was no direct evidence about the structure of the sulfurcontaining molecules included in the deposit.The CoFe magnetic alloys with 50-70% Fe have the highest magnetic moment of 2.4 Tesla 12 and can be obtained electrochemically in the presence of saccharin as an organic additive. Such CoFe alloy has also very high corrosion susceptibility and when used as a writer element in recording heads it can have detrimental effects on performance. Attempts were made to electrodeposit 2.4T CoFe alloys without additives 13 or by replacing saccharin with another organic additive. 14-16 However, replacing saccharin is a difficult task. It is very often a trade-off between good corrosion resistance on one side, and high stress, roughness, grain size, and coer...

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. © 2003 The Electrochemical Society. All rights reserved.