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BELL SYSTEM TECHNICAL JOURNAL 



small temperature range just below its Curie point, it has a negative 

 temperature coefficient several hundred times as large as the positive 

 coefficient of 2-81 molybdenum-permalloy. By choosing suitable 

 compositions and percentages of such compensating alloys, the net 

 temperature coefficient of permeability of a core can be adjusted to any 

 reasonable value, positive or negative, over a desired temperature 

 range. Figure 7 shows a permeability vs. temperature curve for a 



140 



130 

 120 



no 



100 

 90 



K 80 



CO 



< 70 



UJ 



5 



S 60 



Q. 



50 

 40 

 30 

 20 

 10 



100 200 500 



FLUX DENSITY IN GAUSSES 



2000 



5000 



Fig. 6 — Permeability-induction characteristics. 



core stabilized to give a small negative coefficient, compared to a 

 similar curve for a core not stabilized. 



Core Losses 



The desirability of core materials increases in general as their loss 

 characteristics decrease. Low total eddy-current and hysteresis 

 losses give low contributions to attenuation. Hysteresis loss is 

 frequently of especial importance because it appears fundamentally as 

 a resistance which varies with coil current, and because it incidentally 

 generates harmonic voltages. A low value of hysteresis loss thus 



