Spin polarized transport current in n-type co-doped ZnO thin films measured by Andreev spectroscopy

摘要

We use point contact Andreev reflection measurements to determine the spinpolarization of the transport current in pulse laser deposited thin films ofZnO with 1% Al and with and without 2%Mn. Only films with Mn are ferromagneticand show spin polarization of the transport current of up to 55 $\pm$ 0.5% at4.2 K, in sharp contrast to measurements of the nonmagnetic films without Mnwhere the polarization is consistent with zero. Our results imply strongly thatferromagnetism in these Al doped ZnO films requires the presence of Mn.