THE PHYSICAL BASIS OF FERROMAGNETISM 



35 



magnetization, and Einstein and de Haas ^* performed the experiment 

 in 1915. It was repeated in 1918 by Stewart ^^ who for the first time 

 obtained a result consistent with Barnett's, and has been confirmed 

 since by a number of others. 



FINE SUSPENSION 



INDUCTION SOLENOID 



SPECIMEN (R0T0R,M) 

 AND MAGNETIZING 

 COIL 



ADJUSTABLE 

 RESISTANCE, R 



TORQUE COIL, B 



PERMANENT 

 MAGNET 



Fig. 20 — Schematic diagram of the method of determining the gyromagnetic ratio. 



In recent years the method most often used (rotation by magnetiza- 

 tion) is that due to Sucksmith and Bates. ^^ As modified by Barnett,^^ 

 it is shown diagrammatically in Fig. 20. A rod of the material under 



24 A. Einstein and W. J. de Haas, Verh. d. D. Phys. Ges., 17, 152-170 (1915); 18, 

 173-177 (1916); 18, 423-443 (1916). 



26 J. Q. Stewart, Phys. Rev., 11, 100-120 (1918). 



26 VV. Sucksmith and L. F. Bates, Proc. Roy. Soc, 104A, 499-511 (1923). W. 

 Sucksmith, Proc. Roy. Soc, 108 A, 638-642 (1925). 



27 S. J. Barnett, Rev. Mod. Phys., 7, 129-166 (1935). This article and the one 

 in Phys. Zeits., 35, 203-205 (1934) give a good account of the history, methods and 

 results to date. 



