MOLYBDENUM PERMALLOY FOR INDUCTANCE COILS 



391 



0.2 



-0.2 



-50 -25 25 50 



DC MAGNETIZING FORCE IN OERSTEDS 



Fig. 4 — Residual effect of d-c. magnetization on initial permeability — measured three 

 minutes after release of direct current. 



precision filters, to insure that changes in transmission level do not 

 produce serious alterations in the frequency discrimination character- 

 istics. Figure 6 shows the superiority of the new material over the 

 earlier permalloy. 



A new requirement for cores has been introduced by quartz crystal 

 filters used in wide-band carrier systems. In order to secure the neces- 

 sary precision in this type of filter, measures have to be taken to pre- 

 vent departures from the initial frequency adjustment due to changes 

 in core permeability ordinarily occurring with room temperature 

 changes. Extremely small temperature coefificients of permeability 

 have now been achieved by adding to the new 2-81 molybdenum- 

 permalloy powder a very small percentage of special permalloy powder 

 having a molybdenum content of about 12 per cent. Such an alloy 

 has a non-magnetic or Curie point close to room temperature, and for a 



100 

 90 



t± 



5Z 



40 



30 40 



50 60 70 80 90 

 INITIAL PERMEABILITY 



100 110 120 130 140 



Fig. 5 — Effect of superposed magnetization on permeability. 



