614 



BELL SYSTEAf TECHNICAL JOURNAL 



Ml'.TALS 



The metallurgical group, as far as chemical investigation is concerned, 

 is in charge of J. E. Harris. One of his principal interests is the pro- 

 duction in varied forms of special magnetic materials, illustrated by 

 permalloy and perminvar. The field of magnetic materials has been 

 so intimately connected with the fundamental physical theory of ferro- 

 magnetism that the primary responsibility for these investigations has 

 been lodged in a physical research group, the members of which have 

 been responsible for fundamental inventions in this connection. The 



Fig. 4 — Pouring a metallic melt in vacuum by tilting a high-frequency induction 



furnace. 



problems of fabrication and composition control in the experimental 

 work in this connection have, however, afforded much opportunity for 

 the ingenuity of chemists. 



A particular case in point is that of the production of brittle forms of 

 such special magnetic materials, the object being to permit the grinding 

 of the metal into a coarse dust. The dust particles are then insulated 

 by deposition of a film on their surfaces and are pressed into rings which 

 form the cores of modified Pupin-type loading coils. This unusual objec- 



J 



