Direct determination of Hall mobility of photoelectrons in the ferromagnetic semiconductor EuO

The importance of applying the pulsed Redfield technique in the direct determination of the Hall mobility μH of photocarriers in ferromagnetic semiconductors is exemplified, for the first time, by using pure EuO crystals. The value of μH is obtained directly from the measurement of the Hall angle θ = μHB/c, where B is the magnetic induction and c is the light velocity. Thus, it is shown that a large negative-magnetoresistance effect in undoped EuO crystals near the Curie temperature Tc can be attributed mainly to the mobility change. The photocarriers are identified to be electrons, and a mobility value as high as 250 cm2/V sec is observed at 26 °K.