580 THE BELL SYSTEM TECHXICAL JOURNAL, MAY 1954 



upon propagation. Here, as in the earlier optical cases, the disturbances 

 considered are essentially plane wa\'es. In recent j^ears, with the ex- 

 tensive development of microwave techniciues, two gyromagnetic media 

 have been investigated using guided waves. One of these is the gas dis- 

 charge plasma, an ionic medium like the ionosphere, in which, however, 

 the charge density may be varied over wide ranges in a controllable 

 manner. The magnitude of the effects observed in such ionic media are 

 governed by the relation of the applied frequenc}^ to the cyclotron fre- 

 quency of the ions in the dc magnetic field. Goldstein and his associates^ 

 have studied the propagation of waves in a cylindrical wa\'eguide within 

 which a discharge is supported and to which a longitudinal magnetic 

 field is applied. Among many effects which they have obser-\-ed is a 

 large Faraday rotation. 



The other medium being actively investigated is the low-loss ferro- 

 magnetic medium, as exemplified by the ferrites. In this case the pe- 

 culiarities of the medium have their origin in the precession of the 

 magnetization of the ferrite about the applied field. This precession 

 takes place with a frequency dependent upon the applied field strength 

 and large changes in the nature of the propagation occur when the fre- 

 quency of the r.f. applied field approaches this. Polder'- worked out the 

 effective properties of such a medium for plane waves and Hogan^ has 

 made various experimental studies of the propagation in C3dindrical 

 guides containing ferrite. Here, again, Faraday rotation and other 

 non-reciprocal effects have been observed. 



In this paper a variety of topics associated with the theory of guided 

 waves in gyromagnetic media is considered, with the main emphasis laid 

 on the ferrites. The exposition does not attempt to be systematic. A'ery 

 few problems in this field admit of a thorough analytic treatment and, 

 frequently, the more closely allied they are to the practical uses of ferrites 

 in microwave devices the more fragmentary is the anal3^sis. On the other 

 hand since the problems can always be formulated it is always possible 

 in specific cases to resort to a purely numerical solution. The problems 

 considered here all arise in the effort to analyze the operation of various 

 devices and different idealizations are utilized in particular cases. 



In Part I the general properties of gyromagnetic media are discussed 

 and the connection between tRe phenomenological constants of the 

 medium and the underlying molecular model is derived for the ferrite 

 and for the plasma. The assumptions necessary to render the ferrite 

 problem tractable are discussed at some length. Maxwell's equations are 

 written down for a general gyromagnetic medium and some of the salient 

 features of their solution are noted. The propagation of circularly po- 



