THE MICROWAVK GVKATOR 



11 



stance, is given by the expression (n + K), and not by the usual perme- 

 ability, bx/hx = iJL. It is also apparent that the quantity fi -\- K can 

 vary over wide limits in the vicinity of the ferromagnetic resonance. 

 For this reason, care must be taken in interpreting permeability data 

 for ferromagnetic materials which now occur in the literature and which 

 were obtained by means of impedance measurements at microwave 

 frequencies, since the above equations indicate that this method does 

 not measure the same quantity that is measured at low frequencies by 

 means of a toroidal sample overwoiuid with two coils. The low fre- 

 quenc}' measiu'ement of permeability obviously measures the quantity 

 which is designated as m in Ecjuation (8). 



If Equations (11) and (12) are solved for the attenuation constants, 

 a± , and the phase constants, jS± , the following results are obtained: 



^^ ^co ^/{^' ±K')e' 



< /|/ (1 + tan 5,„[4 tan 8d + tan 5^(1 + tan- 8d)] + tan- 8d 



— 1 — tan 8m tan 8d 



and 



/3± = 



where : 



tan 8m = 



(13) 



(m' ± K')e' 



(1 + tan 8m[4: tan 8d + tan 5„(1 + tan- 8d)[ + tan ^ 8d 



+ 1 + tan 8m tan 8d 



(14) 





(The + sign must be used for a positive circularly polarized wave; 

 the negative sign for the negative circularly polarized wave.) 



tan 8d = —r = dielectric loss tangent 



e = e' — je" = complex dielectric constant 



