1338 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1953 



vector of the wave is parallel to the magnetization the torque on the elec- 

 trons is zero and the wave sees an isotropic dielectric medium with 

 relative permeability equal to unity. However^ when the electric vector 

 is parallel to the magnetization the magnetic vector is at right angles to 

 it and can set the electrons into precession. 



Consider a wave propagating in the x direction in an infinite medium 

 magnetized in the z direction. Let this wave be polarized so that it has 

 components Eg and hy. When this wave enters the magnetized medium, 

 hy exerts a torque on the magnetization vector M causing it to precess 

 about the z axis. This results in both an rriy and an Mx component of 

 alternating magnetization. There is, however, no component of b in 

 the X direction because of internal demagnetizing fields arising from an 

 effective volume distribution of magnetic charge as shown in Fig. 3. 

 Such a volume distribution of magnetic charge arising from the periodic 

 reversal in phase of the driving magnetic field is propagated through the 

 medium at the velocity 



V = 



VJS 



An instantaneous picture of this distribution is shown in Fig. 3. The 

 magnetic poles set up a magnetic field in the x direction throughout the 

 material. This field is commonly called a demagnetizing field and for 



N S S ^ S S N 



N NS Ss^^S SN N 



NN SSS^SSS NN 



N S S s S s N 



N ^ ^ S ^ S ^ S ^ ^ N 



s s s 



^NNSS^SSS^SSNN*^ 

 N S s S s S N 



NN SSS^SSS NN 



N S ^ ^ S S N 



N ^ ^ ^ S ^ S ^ ^ " "^ 



^ N N S s ^ S 3 S ^ S S N N '^ 



N S s 3 s S N 



NN SSSSSSS NN 



N S S S s s N 



= s ^ t = s ^ 



s s s 



s 



s 



'^ N N S 3 S 3 S 3 S 3 S N ^ N 



Fig. 3 ~ EflFective volume distribution of magnetic poles arising from phase 

 reversals in transversely magnetized infinite medium. 



