Effect of Nb concentration on the spin-orbit coupling strength in Nb-doped SrTiO3 epitaxial thin films

Seong Won Cho,Milim Lee,Seungwu Han,Kanghoon Yim,Sungmin Woo,Suyoun Lee,Woo Seok Choi

doi:10.1038/s41598-018-23967-2

Abstract

Several oxide materials have attracted much interest for the application in spintronic devices due to unusual properties originating from the strongly correlated orbital and spin degrees of freedom. One missing part in oxide spintronics is a good spin channel featured by strong spin-orbit coupling (SOC) which enables an efficient control of the electron’s spin. We have systematically investigated the dependence of the SOC strength of Sr(NbxTi1−x)O3 thin films on Nb concentration (nNb = 2~20 at. %) as a deeper exploration of a recent finding of the strong SOC in a heavily Nb-doped SrTiO3 (Sr(Nb0.2Ti0.8)O3) epitaxial film. Apart from a finding of a proportionality of the SOC to nNb, we have observed an intriguing temperature dependence of the SOC strength and the anisotropic magnetoresistance (MR) in the intermediate nNb region. These phenomena are associated with the temperature dependence of Landé g-factor and the change of the band structure, which is consistent with the result of density functional theory (DFT) calculation.

Highlights

Electronic devices based on conventional semiconductors are facing the limit of evolution due to the huge consumption of energy, generation of excessive heat, monotonic functionality, and inextensible miniaturization
We found that a heavily Nb-concentration split SrTiO3 (Nb)-doped SrTiO3 (SrNb0.2Ti0.8O3) epitaxial film grown on STO showed the strong spin-orbit coupling (SOC) and the high carrier mobility – ideal characteristics for a good spin channel – which resulted in a large linear magnetoresistance (LMR)[17]
We have performed a systematic study on the magnetotransport properties of SrNbxTi1−xO3 films with varying Nb concentration in the range of 2~20 at. % to find that the magnetotransport property is dominated by three-dimensional weak antilocalization (WAL)[18,19] and that the SOC strength is proportional to nNb

Summary

Introduction

Electronic devices based on conventional semiconductors are facing the limit of evolution due to the huge consumption of energy, generation of excessive heat, monotonic functionality, and inextensible miniaturization. (a~e) Magnetoresistance (MR) vs B curves of Nb:STO epitaxial films with varying Nb concentration (nNb) at various temperatures.

Results

Conclusion