1160 THE BELL SYSTEM TECHNICAL JOURNAL, SEPLEMBER, 1953 



10* 



10 



/iQ MnZn FERRitE 



'/ZQ NL Zn FERRITE 



^-^ //Q CARBONYL IRON 

 POWDER (// = 13) 



\ V---//Q Mo PERMALLOY 

 POWDER (// = 14) 



JJ.Q 0.001" 4-79 

 Mo PERMALLOY 



// FINE METALLIC POWDER 



10-1 



10 102 10^ 



FREQUENCY IN KILOCYCLES PER SECOND 



10^ 



105 



Fig. 2 — Comparison of the frequency variation of fx and nQ for ferrites and 

 other magnetic materials. 



may be described. This comes about because the ferrites, in which the 

 new effects are observed, have both dielectric and magnetic properties. 

 The material is most conveniently described in terms of two complex 

 quantities: the permeability, fi = fi' — jfx" , and the dielectric constant, 

 e = e' — je" . n' corresponds to the usual low frequency permeability and 

 Q = ii! I\i" . Similarly e' corresponds to the usual low frequency dielectric 

 constant, while e'Ve' = tan 5, the loss tangent of the material. Thus 

 the quantities y." and e" are measures of the magnetic and dielectric 

 losses per cycle respectively, in the material.^ The fact that m" and e" 

 represent loss per cycle means that much higher values of these quantities 

 can be tolerated at low frequency than at microwave frequencies. 



At frequencies above a few megacycles, it becomes very difficult to 

 make meaningful observations on wound toroidal cores. Such difficulty 

 may be overcome by making measurements on a toroidal sample placed 

 in a coaxial line. Details of the experimental procedure may be found 

 in references 9 through 12. The same procedure may be applied at micro- 

 wave frequencies with waveguide used instead of coaxial line. In this case. 



