Magnetic Alloys of Iron, Nickel, and Cobalt * 



By G. W. ELMEN 



The unexpected magnetic properties of certain alloys of iron and nickel 

 discovered some 20 years ago led to a thorough study of the entire range of 

 iron-nickel alloys. The results of this study were so encouraging that 

 alloys of these metals with cobalt, the only other ferromagnetic metal, also 

 were studied, as well as various alloys of these metals with small amounts 

 of non-magnetic metals added. From the results of this extended investi- 

 gation have emerged several alloys that are playing important parts in the 

 continued advancement of electrical communication. 



SOME 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 instru- 

 mentalities and circuits of electrical communication, and were devel- 

 oped 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 charac- 

 ter 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 non- 

 magnetic 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. One of 

 the first and most striking applications was to submarine telegraph 

 cables. The largest field of application, however, has been in teleph- 



* Published in the December 1935 issue of Electrical Engineering, and scheduled 

 for presentation at the Winter Convention of the A. I. E. E., New York City, Janu- 

 ary 28-31, 1936. 



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