Conductivity of high-mobility epitaxial GdN

TL;DR

This study investigates the electron transport properties of high-quality epitaxial GdN films, revealing enhanced mobility and detailed magnetic and electronic characteristics, contributing to understanding lanthanide nitride conductivities.

Contribution

It presents the first epitaxial GdN films with improved crystallinity and mobility, providing detailed magnetic and transport measurements that advance the understanding of GdN's electronic behavior.

Findings

GdN exhibits ferromagnetic transition at ~70 K.

Mobility is significantly higher than in previous films.

Doping by nitrogen vacancies introduces ~3×10^{20} cm^{-3} electrons.

Abstract

We report electron transport studies of a (001) GdN film grown on the square net presented by the (001) surface of LaAlO3, motivated by recent advances in epitaxial thin-film growth of several lanthanide nitrides. The film we have grown for the purpose is characterised by in-situ RHEED and ex-situ XRD and XRR to show the best crystallinity and smoothest surfaces we have accomplished to date. It shows a clear ferromagnetic transition at $\sim70$ K with a saturation magnetisation within uncertainly of 7 $\mu$B/Gd$^{3+}$ ion, a remanence of 5 $\mu$B/Gd$^{3+}$ ion and a coercive field of $\sim$5 mT. It is doped by $\sim1$% nitrogen vacancies that introduce $\sim3\times10^{20}$ cm$^{-3}$ electrons into the conduction band. The resistivity shows transport in a conduction band doped to degeneracy by $\sim0.01$ electrons/formula unit with a residual resistance ratio of 2 and a Hall resistivity permitting easily-separated ordinary and anomalous Hall components. The mobility is an order of magnitude larger than we have found in earlier films.