Anisotropy Sources for Electrodeposited Permalloy Films

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Abstract
Experimental evidence has been found to indicate that electro‐deposited iron‐nickel films are sensitive to the geometric anisotropy of the chain‐like growth of crystallites that compose the conducting film of the substrate. Chromium‐gold films were vacuum evaporated on glass slides at normal and oblique incidence. Fired gold films were also made to be used as examples of minimum geometric anisotropy. Using Wolf's solution as an electrolyte, Permalloy films were electrodeposited, some with an some without a magnetic field. Uniaxial anisotropy was found for all the specimens, including the controls, with the exception of those specimens plated without a magnetic field on both, normal incidence substrates, and fired gold substrates. Angles as small as 2° were found sufficient to induce a marked anisotropy. From the knowledge that evaporation at oblique incidence creates a geometric anisotropy by a process of self‐shadowing of the crystallites, it is believed that this geometric anisotropy is replicated in the magnetic film as a shape anisotropy which in turn induces a magnetic anisotropy. In support of this theory, directional polishing of the substrates was also found to induce an anisotropy, although in these cases usually with higher HK values. The epitaxy model can be helpful for applying data from evaporating techniques to plating techniques. Magnetic films in this study averaged 3000 A in thickness. The B—H tests were made at 400 cps. Conclusions are that, in this experiment, the anisotropy induced by the magnetic field can be separate from the one induced by the substrate, and sensitivity to geometric anisotropy is pronounced.

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