1334 THE BELL SYSTEM TECHNICAL JOUliXAL, XOVEMBEU 1957 



the 60-cycle characteristics of the axial and circular flux versus axial 

 drive and the switching voltage waveforms under pulse conditions are 

 given in Fig. 11 for 2-mil wire of composition 83 Ni, 17 Fe. 



Note the negative prespike on the switching waveforms. By simultane- 

 ous observation of both the axial and circular switching voltage wave- 

 forms on many different magnetic wires it has been concluded that the 

 negative prespike is due to an initial coherent rotation of the magnetiza- 

 tion vector which results in an initial increase in the circular flux com- 

 ponent. It is during this coherent rotation that the normal positive pre- 

 spike on the axial switching voltage waveform is observed. Because of 

 the mechanically introduced strain anisotropy, however, the magnetiza- 

 tion A'ector is constrained to remain nearly parallel to the easy direction 

 of magnetization. Thus, the coherent rotation soon ceases and the re- 



ABRUPT INCREASE 

 N NOISE 



to 

 Q 



UJ 



I- 

 10 



a. 



LU 



o 



0. 



o 

 o 



I 



20 



40 60 80 100 



ImaGNETiC 'N MILLIAMPERES 



120 



140 



Fig. 12 — Range of writing currents for 83 Ni, 17 Fe wire operated mode. A 

 Read drive held constant at 9 oersteds. Tjpical signal-to-noise ratio for a read 

 is indicated. 



