Electrons and Positrons in Amorphous Mg70Zn30

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Abstract
Measurements of the Compton profiles and angular correlations of positron annihilation radiations on the amorphous Mg 70 Zn 30 alloy are carried out. From the Compton profile measurement it is found that the valence electrons are free-electron like and the Fermi momentum is 0.77 ±0.02 atomic units ( k F =1.46 ±0.02 A -1 ) in agreement with the value calculated from a simple electron gas model. The angular correlations of positron annihilation radiations measured at 80 K and 300 K show significant smearing of the break at the Fermi momentum. The smearing at 80 K is heavier than that at 300 K. The smearing is found to be caused by localization of the positron. The potential for localization of the positron is much shallower and wider than that due to a vacancy in crystalline materials. The positrons are localized in low density dilated regions of the amorphous structure.

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