1160 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 195-1: 



91(^0) 



.^.^^^ 2 



8 



(n-i);?- (n-;^)77 



r\TT 



(n + -j)77 (n+i);7 



Fig. 6 ■ — Rotation gain, gi{Oa), versus electrical thickness, Bq , for small mag- 

 netization. 



Perturbation theory enables us to solve approximately, for weak mag- 

 netization, the problem just considered for the case in which a right 

 circular cylinder of ferrite snugly fits a cylindrical waveguide. We will 

 show that, "\\ith a suitable reinterpretation of the constants, equation 

 (22) for the rotation gain of the extended slab continues to apply here. 



Before magnetization, a particular right circularly polarized mode, 

 say the rri , is present in the sample. The small magnetization distorts 

 the pattern of this mode and changes the propagation constant slightly. 

 The distorted pattern can be expanded in the series of normal modes of 

 the unperturbed material. In these expansions only the coefficient of the 



