The preparation and properties of magnetoresistive permalloy films

The magnetoresistive and magnetic properties of evaporated permalloy films, such as those used to sense magnetic bubbles, are influenced by the deposition conditions. An elevated substrate temperature produces the largest fractional change in resistivity but results in high dispersion, which may be unsatisfactory for device applications. Decreasing the iron content from the commonly used 81-19 Ni-Fe composition increases the fractional change in resistivity but also results in increased coercivity. The most useful films have the 81-19 composition and are produced at moderate temperatures of 200 to 250°C. Electrical continuity of such films can be maintained down to thicknesses of less than 100 A{ring operator}. © 1973 American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc.