ABSTRACTS OF TECHNICAL ARTICLES 319 



provided that the area of the outer oxide surface remains constant. 

 (6) The conductivity of the oxide varies with the time of sending cur- 

 rent through the oxide. (7) The conduction current in the oxide 

 obeys Olim's hiw and does not saturate even though its value is 

 hundreds of times hirger than the saturated emission. (8) The oxide 

 acquires a positixe potential with respect to the core regardless of 

 whether the space current is limited by space charge or by emission. 

 This potential varies linearly with the space current drawn to the 

 plate and is of the order of a few tenths of a volt. (9) The emission 

 for the optimum amount of barium on the oxide surface depends upon 

 the pre\'ious treatment of the oxide. From these results we conclude 

 that: (1) The active layer is at the outer oxide surface. The activity 

 depends on the concentration of barium and oxygen on this surface 

 and also upon the amount of metallic barium dispersed through the 

 oxide. The core material does not directly affect the emission but it 

 does greatly affect the ease with which free barium is produced by heat 

 treatment or electrolysis. (2) The thermionic electrons originate in 

 the oxide just underneath the adsorbed barium. (3) Most of the 

 current through the oxide is conducted by electrons, a small portion 

 being carried by barium and oxygen ions. 



Barkhaiisen Effect: Orientation of Magnetization in Elementary 

 Dofnains.^ Richard M. Bozorth. Brief mention is made of previ- 

 ously published work on the nature of the discontinuities in mag- 

 netization discovered by Barkhausen in 1919. Including the recent 

 results described in this note, the experimental data now indicate that 

 changes in the magnetization of ferromagnetic materials occur in the 

 following way: The material is composed of small regions or "ele- 

 mentary domains" (of the order of 10~* cm.^), each of which is gener- 

 ally magnetized to saturation in a different direction. As the strength 

 of the applied magnetic field increases, the magnetization in some of 

 the domains changes suddenly from saturation in one direction to 

 saturation in another direction associated with less potential energy. 

 The change in each domain gives rise to a single click in the telephone 

 receiver which terminates the apparatus usually used to observe the 

 etYect. In annealed materials in which the crystal grains are much 

 larger than the domains, the direction of magnetization within each 

 domain depends on the orientation of the crystal grain in which it is 

 situated, and coincides with its direction of easy magnetization as 

 determined by separate experiments on large single crystals. 

 3 Phys. Rev., January 15, 1932. 



