MAGNETIC MATERIALS IN RELATION TO STRUCTURE 23 



ductivity in this region at room temperature is greater than that of 

 either of the components. The anomalous behavior was attributed 

 several years ago by one of the authors,^^ not to compound formation, 

 but to a "peculiar solid solution." Kussman, Scharnow and Schulze -^ 

 in a recent paper attribute the effects to the formation of superstructure 

 in the body centered lattice which exists at this point. This, in a sense, 

 is an extension of the earlier explanation. Here again, it appears that 

 further work is warranted and is required before the structure is 

 completely understood. 



In connection with the metallurgy of the 50-50 iron-cobalt alloy, 

 there are some interesting considerations. The binary alloy can be 

 worked hot, but is extremely brittle when cold. This imposes definite 

 limitations where thin sheet produced by cold rolling is required. The 

 limitation can be overcome by adding a few percent of vanadium ^^ to 

 the composition. This alloy can be worked hot, and after a quench 

 from a high temperature, also can be cold-rolled to thin sheet. The 

 magnetic characteristics are not greatly afifected by the vanadium, 

 provided the addition is small. 



The structural changes resulting from the additions of vanadium are 

 not clearly understood. It is known that vanadium retards the trans- 

 formation which occurs in these alloys at approximately 900° C. and 

 therein lies a possible explanation for its action. The high temperature 

 modification is malleable as shown by satisfactory hot working prop- 

 erties. By quenching, sufficient of this modification may be preserved 

 at room temperature, when vanadium is present, to permit cold rolling. 



Iron- Cobalt -Nickel Alloys 



In the ternary system, iron-cobalt-nickel, is a region in which the 

 alloys exhibit an unusual and useful property, namely, constant perme- 

 ability in low fields. Because of this characteristic, alloys in this region 

 have been named perminvars.^^ A typical alloy with marked permin- 

 var characteristics contains 45 per cent nickel, 25 per cent cobalt and 

 30 per cent iron. The effects of heat treatment are illustrated in Fig. 

 1 1 . The effect on the magnetization curve of air quenching, annealing, 

 and baking at a low temperature is shown for this typical alloy. The 

 extension of constant permeability to higher magnetizing forces by a 

 low temperature bake is clearly demonstrated. 



The constancy of permeability in perminvar has been explained in 

 one hypothesis as due to the presence of two constituents in the alloy, 

 one a soft magnetic material, the other a hard magnetic material. The 

 experimental evidence for this hypothesis is derived largely from the 

 constricted hysteresis loops which are obtained for these alloys after a 



