CrI3 magnetic nanotubes: A comparative DFT and DFT+U study, and strain effect

Artem V Kuklin,Maxim A Visotin,Woohyeon Baek,Paul V Avramov

doi:10.1016/j.physe.2020.114205

Abstract

Abstract In this paper, structural and electronic properties of CrI3 magnetic nanotubes (NTs) are studied using density functional theory. Both armchair and zigzag CrI3 nanotubes demonstrate a high correlation in strain energy between each other independently on accounting the Hubbard correction. The strain energies decrease with expansion of the tube diameter making the tubes’ synthesis with a diameter larger than 45 A to be energetically possible. The nanotubes of both zigzag and armchair chirality are ferromagnetic semiconductors with band gaps close to that of the CrI3 monolayer. The band gaps are suppressed by reducing the tube diameters due to the structural stress leading to deformation of the Cr–I crystal field and changes in the bond lengths. The external strain can be utilized to flexibly tune the electronic properties of CrI3 nanotubes with the desired spin-up/spin-down band gap ratio. Strong distortion of the octahedral Cr–I crystal field under compression results in nontrivial behavior in the spin-up band gap of (4, 4) tube. Stretching of tubes leads to the enhancement of the exchange energy that should result in higher Curie temperature, therefore providing a good platform for potential applications in spintronic nanodevices.

Highlights

Discovery of carbon nanotubes (CNTs) [1] and their following intensive investigations led to a new field in condensed matter physics represented by one-dimensional objects
COMPUTATIONAL METODS The electronic structure calculations were performed using density functional theory (DFT) [30,31] within GGA PBE [32,33] exchange functional and Hubbard correction (GGA + U) [34,35] in the form realized in Vienna Ab-initio Simulation Package (VASP) [36,37]
The results suggest that nanotubes of both chiralities are ferromagnetic semiconductors with the band gaps close to that of the monolayer

Summary

INTRODUCTION

Discovery of carbon nanotubes (CNTs) [1] and their following intensive investigations led to a new field in condensed matter physics represented by one-dimensional objects. The first inorganic nanotubes successfully obtained from complex layered compounds such as WS2 and MoS2 reported by Tenne [8,9]. Similar to transition metal dichalcogenides the CrI3 monolayer could be folded into a nanotube preserving of its magnetic order and generating new one-dimensional ferromagnetic materials for valuable nanoelectronic applications. The strain energies of CrI3 nanotubes of both chiralities are in a high correlation with their diameters independently on the Hubbard correction. Both types of nanotubes are ferromagnetic semiconductors with the band gap width close to that of the monolayer. Applying strain to the tubes one can flexibly vary the band gaps and exchange energies

COMPUTATIONAL METODS

RESULTS AND DISCUSSION

CONCLUSIONS