MOTION OF IXDIVIDIAL DOMAIN' WALLS 



1025 



ing as expected. There was an additional contiibution, however, which 

 Kittel suggested was due to mechanisms of the sort which give rise to 

 the width of ferromagnetic resonance hnes. These mechanisms of course 

 are the controlhng ones in the ferrites, where eddy current losses are 

 small. The motion of a domain wall damped by such effects and un- 

 affected by eddy currents was first discussed in a classic paper by Landau 

 and Lifshitz. 



The experiments reported in the present paper consist of measure- 

 ments of the velocity of a movable wall as a function of applied magnetic 

 field in a sample like that shown in Fig. 1 . The measurements are made 

 by observing the voltage induced in a secondary winding on such a 

 sample when a knoAvn field is applied by means of a pulse of current 

 in a primary winding. The composition of the ferrites used in these 

 studies is given by the approximate chemical formula (NiO)o.75(FeO)o.26- 

 Fe203 . Data have been taken as a function of temperature on several 

 samples. The large, perfect crj'stals of the ferrites which are essential 

 to the success of these experiments have been obtained through Dr. 



POSITIONS OF 

 ' DOMAIN WALLS 



Fig. 1 — Sample of fcrrite used in this study. 



