MAGNETIC ALLOYS OF IRON, NICKEL, AND COBALT 445 



The group of alloys of high permeability for low magnetizing forces 

 in the iron-nickel series we have named permalloy.^ The permalloys, 

 therefore, include nickel-iron alloys containing more than approxi- 

 mately 30 per cent nickel. In referring to specific compositions in 

 this group we have found it convenient to use as a distinguishing prefix 

 for each composition its nickel content. For example, 78.5 permalloy 

 is the alloy containing 78.5 per cent nickel and 21.5 per cent iron. 

 When other elements are added to the permalloys, " the chemical 

 symbol and the percentage of the added element are also added to 



Fig. 6 — Hysteresis losses, ergs per cm.^ per cycle, for maximum flux density 

 of 5,000 gauss for annealed alloys. 



the prefix. For example, 3.5-78.5 Mo-permalloy is an alloy containing 



3.5 per cent molybdenum, 78.5 per cent nickel, and 18 per cent iron. 



The ternary alloys of constant permeability and extremely low 



hysteresis loss at low flux densities we have also grouped together 



under a common name, perminvar.^ The limits of composition for 



the perminvars are less easily defined than for the permalloys, because 



the transition in magnetic properties is not as marked with small 



^ H. D. Arnold and G. W. Elmen, Journal of Franklin Inst., May, 1923, p. 621. 

 ' G. W. Elmen, Journal of Franklin Inst., Sept., 1928, p. 317. 



