THE MICROWAVE GYRATOR 15 



hibitive, it is wise to then raise the appHcd field to some high value, 

 so that the resonance freciuency will fall well above the operating fre- 

 ({uency. Thus, for many cases of interest it is possible by various means 

 to place the ferromagnetic resonance absorption frequency sufficiently 

 far from the operating fre(}uen(;y so that magnetic losses due to this 

 phenomenon are negligible.* The data accumulated to date indicate 

 that the major component of the magnetic losses at microwave fre- 

 quencies is due to this phenomenon. Only in a few cases have data been 

 taken which have indicated that other factors, such as domain wall 

 relaxation, contribute to the magnetic loss at microwave frequencies. 



If then, the magnetic field is controlled so that the ferromagnetic 

 resonance absorption is negligible, Equations (13) and (14) can be 

 simplified to: 



^^^.^^^pl ^yj + j^„,,__i (18) 



and : 



(19) 



is: 



""//SZZ v^7^:r (20) 



which can be written as: 



«± 

 and 



fc = " 4/'^^' V7^:r (21) 



where /x' and K' are given in the appendix. 



If Equation (21) is now inserted into Equation (15) a formula for 

 rotation is obtained which is valid within the limits of the above ap- 

 proximations. If in addition, the frequency of the wave is sufficiently 

 greater than the resonance frequency, so that: 



CjOr.s « CO (22) 



then Equation (15) takes the particularly simple form: 



P _ CO 



f ~ 2c 



i/'^T/'+'-^V- 



47rM^7 



(23) 



Most ferrites saturate at 2,000 gauss or less. Hence, for a frequency of 



* This is not always possible, for some ferrites, in the polycrystalline state, 

 exhibit extremely broad ferromagnetic resonance absorption lines and it is diffi- 

 cult to operate at anj' frequency without apprecialilo absorption. 



