THE PHYSICAL BASIS OF FERROMAGNETISM 



11 



The behavior of the line when subjected to a field H may be found 

 by adding to W\ the energy term — HyLA cos (^o — B), where do is the 

 angle between the line of centers and the direction of the field, and 



FIELD STRENGTH 



Fig. 7 — A magnetization curve and hysteresis loop for an infinite line of 

 equally spaced magnets originally "demagnetized." 



finding the value of 6 which makes this total energy a minimum for 

 given values of ^o and H: 



j-Q^W, - IIixA COS (do - 9)'] = 0. 



This gives 



II = 



idide)Wi 



IXA sin {do — d) 



