Large magnetic effect on photothresholds in doped EuO

Generally, a magnetic phase transition has very little influence on photoemission. It was found that this does not apply to doped EuO, by measuring the photoelectric yield Y of pure and doped EuO single crystals up to 10 eV both above and below the ferromagnetic transition. For pure EuO the photothreshold changes only very little. In contrast, for EuO doped with approximately 1 percent La, it shifts by as much as 0.5 eV on going through T/sub c/. An interpretation of the results is attempted in terms of a change of the vacuum level of doped crystals at the magnetic phase transition. (auth)