Polarization of Positrons and Annihilation in Ferromagnetic Materials

Publisher Website
Google Scholar
Abstract
The angular correlation of two-quantum radiation from annihilation of positrons in ferromagnetic media has been investigated as a function of the direction of magnetization. The observed changes in the correlations are attributed to the polarization of positrons emitted from an unpolarized source. In the part of the two-quantum correlation associated with large electron momentum, the yield is greater when the polarization of the positrons is parallel to the magnetic field and it is less when the field is reversed. This effect is enhanced when the initial energy, and hence the polarization, of the positrons increases. The qualitative features of the effect were the same in three samples of iron (one containing a large amount of cobalt). No effect was detected for nickel or gadolinium (below the Curie point), and none for any nonferromagnetic metal which was used as a test of the experiment.