Spin-related magnetoresistance of n-type ZnO:Al and Zn_{1-x}Mn_{x}O:Al thin films

TL;DR

This study investigates the spin-related magnetoresistance in n-type ZnO:Al and Mn-doped ZnO thin films at very low temperatures, revealing the roles of spin-orbit coupling and s-d exchange interactions.

Contribution

It provides a quantitative analysis of spin-orbit coupling in ZnO:Al and introduces a model explaining complex magnetoresistance in Mn-doped ZnO related to magnetic polarons.

Findings

Determined the spin-orbit coupling constant 4_{so} for ZnO:Al.

Interpreted large magnetoresistance in Mn-doped ZnO via s-d exchange and magnetic polarons.

Proposed a model explaining magnetoresistance in magnetic oxide systems.

Abstract

Effects of spin-orbit coupling and s-d exchange interaction are probed by magnetoresistance measurements carried out down to 50 mK on ZnO and Zn_{1-x}Mn_{x}O with x = 3 and 7%. The films were obtained by laser ablation and doped with Al to electron concentration ~10^{20} cm^{-3}. A quantitative description of the data for ZnO:Al in terms of weak-localization theory makes it possible to determine the coupling constant \lambda_{so} = (4.4 +- 0.4)*10^{-11} eVcm of the kp hamiltonian for the wurzite structure, H_{so} = \lambda_{so}*c(s x k). A complex and large magnetoresistance of Zn_{1-x}Mn_{x}O:Al is interpreted in terms of the influence of the s-d spin-splitting and magnetic polaron formation on the disorder-modified electron-electron interactions. It is suggested that the proposed model explains the origin of magnetoresistance observed recently in many magnetic oxide systems.