432 



THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 1957 



between the use of a spherical sample and a thin disc, such as the per- 

 turbing effect on the cavity field, the accuracy of small loss measure- 

 ment, the occurrence of resonance at a static field where the intrinsic 

 parameters are not at resonance, and the possibility of making accurate 

 measurements of the electric susceptibility. Therefore, the sphere method 

 and the disc method will be reviewed briefly and an attempt will be 

 made to compare their capabilities. It is hoped that this comparison will 

 also be helpful for the evaluation of other measuring techniques not 

 covered in this paper. 



3.1 The Small Sphere Method 



In order to appreciate the significance of the quantities measured with 

 the small sphere method it is expedient to define an effective suscep- 

 tibility tensor Xms by relating the magnetization vector* to the applied 



^-L=Xg/2— I 



H. 



Fig. 2 — Degenerate TEui cylindrical cavity with ferrite sphere. 



[-- L=Xg/2--| 



H, 



Fig. 3 — Degenerate TEm cj'lindrical cavity with ferrite disc. 



* R. A. Waldron (Institute of Electrical Engineers, Convention Oct. 29 to 



— ♦ 



Nov. 2, on Ferrites, London, 1956) related the magnetic induction vector B in a 



