Magnetic Alloys of Iron, Nickel, and Cobalt

O M E alloys of iron, nickel, and cobalt have remarkable magnetic properties superior in many situations to those of the constituent metals. Many of these alloys have found wide use in the instrumentalities and circuits of electrical communication, and were developed primarily for that purpose. This paper reports the experience and techniques of the Bell Telephone System in the development and utilization of these materials. The advantageous properties of these alloys were disclosed through exhaustive researches, during which the whole realm of combinations of these three metals was explored. That certain alloys of iron and nickel had unexpected properties at low flux densities had already been discovered in the Bell Telephone Laboratories. There was at that time no theoretical basis for predicting, or even explaining, the character of those alloys; and, therefore, a study was undertaken of the whole iron-nickel series. The results were so encouraging that combinations of these elements with cobalt likewise were studied; and finally those alloys of special interest were combined with varying amounts of nonmagnetic metals. In the course of this investigation several thousand specimens were made and tested in a period extending over fifteen years. Such an empirical investigation is time consuming and expensive, but in a field where so little theory was available for guidance it was the only certain means to determine the practical possibilities of these alloys. It has been justified by the large number of alloys it has developed for practical use in communication engineering.