986 THE BELL SYSTEM TECHNICAL JOURNAL, OCTOBER 1951 



Since the permeability is much higher than can be accounted for by 

 domain rotation it is obvious that domain boundary motion is occurring. 

 Hence in determining the domain sizes from the slope of the decrement vs 



Fig. 13— Photograph of domains in a single nickel crystal (after Williams). Field of 

 view, 0.5 mm. 



frequency curve, equations (1) and (2) for domain boundary motion are 

 appropriate. 



When the data of Fig. 12 are extrapolated to zero frequency it appears 

 that there is a microhysteresis loss (which is independent of the frequency) 

 giving a decrement of 0.01. The initial slope of the 8i vs/ curve is then about 



