A REVIEW OF NEW MAGNETIC PHENOMENA 



1157 



portant use in inductors for networks and in transformers in telephone 

 circuits. Magnetic recording tape makes use of 7-Fe203. An increasing 

 amount of information of interest to the design engineer is becoming 

 available in manufacturers' catalogs. 



III. DC CHARACTERISTICS 



For convenience in the following discussion, the frequency range 

 under consideration has been divided somewhat arbitrarily according 

 to the magnetic phenomena which have been observed. We will begin 

 by discussing dc behavior of magnetic materials. 



As far dc magnetic properties are concerned, the modern picture is the 

 same as the classical one. The study of ferrites has revealed no essentially 

 new phenomena, at least so far. 



Hysteresis loops for typical ferrites are shown in Fig. 1, together with 

 loops for iron and for permalloy. It will be observed that some ferrites 

 compare favorably with permalloy with regard to hysteresis loss (pro- 

 portional to the area of the hysteresis loop). Their saturation flux 

 density is considerably lower, the maximum so far obtained being be 

 tween 4,000 and 5,000. 



By applying pressure to a sample and thereby introducing strain, some 

 investigators have found it possible to produce ferrite cores having prac- 

 tically rectangular hysteresis loops,^ just as similar effects have pre- 

 viously been obtained with permalloy and other magnetic material. 



12 - 



CD -4 



•16 



4-79 Mo 

 PERMALLOY 



r 



6-2 2-6 



H IN OERSTEDS 



Fig. 1 — Hysteresis loops of iron, permalloy and typical ferrites. The thin 

 ferrite loop is for a MnZn ferrite, while the larger loop represents a NiZn ferrite. 



