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

TL;DR

This study measures the spin polarization of transport current in Mn-doped ZnO thin films using Andreev spectroscopy, revealing ferromagnetism linked to Mn presence with up to 55% polarization at low temperature.

Contribution

It demonstrates that ferromagnetism and significant spin polarization in Al-doped ZnO thin films depend on Mn doping, using point contact Andreev reflection measurements.

Findings

Mn-doped ZnO films show up to 55% spin polarization at 4.2 K.

Non-magnetic ZnO films exhibit negligible spin polarization.

Ferromagnetism in these films requires Mn presence.

Abstract

We use point contact Andreev reflection measurements to determine the spin polarization of the transport current in pulse laser deposited thin films of ZnO with 1% Al and with and without 2%Mn. Only films with Mn are ferromagnetic and show spin polarization of the transport current of up to 55 $\pm$ 0.5% at 4.2 K, in sharp contrast to measurements of the nonmagnetic films without Mn where the polarization is consistent with zero. Our results imply strongly that ferromagnetism in these Al doped ZnO films requires the presence of Mn.