Magnetization in CNT induced by nitrogen doping and enhanced by transversal electric field application

Density-functional theory (DFT) is employed to study the induced magnetization in nitrogen-doped arm-chair carbon nanotubes (ACNT:N) and assess the effect of application of electric field. Three fashions of dopants' distributions were considered: (i) N-dopant atoms in a sequence of a chain along the ACNT; (ii) N-dopant atoms in alternating position with carbon atoms in a chain along the ACNT; and (iii) N-dopant atoms randomly distributed on the surface of ACNT. The results show that: (a) In absence of electric field, pristine and randomly N-doped ACNTs are paramagnetic. (b) Ferromagnetism/anti-ferromagnetism can be achieved when N-dopant atoms are close like in (sequenced or alternating) chain with number of N-dopant atoms odd/even, respectively. (c) Critical transversal electric field Fc congruent to 2 V/A degrees is needed for bandgap ionization of zigzag CNT (ZCNT) and found to be in excellent agreement with the experimental data. (d) Stronger transversal electric fields, F >= 4 V/A degrees, would be able to induce magnetization in ACNT:N. Assuming z-direction to be along the ACNT axle, then N-atom's P-z orbital would contribute to sigma-bonding whose energies are far deeper away from Fermi energy; so M-z = 0, and (M) over bar = M-x(i) over cap + M-y(j) over cap would always be radical to ACNT:N. The strong transversal field has the ability to tune the contributions of the pi-bond electrons into building up the magnetization causing ferromagnetism and anti-ferromagnetism. Our results are benchmarked to the experimental data and theoretical results available in the literature. The relevance of our work to spintronic and gas-sensing devices is further discussed.

Automated summary

In this study, density-functional theory (DFT) was used to investigate the induced magnetization in nitrogen-doped carbon nanotubes (ACNT:N) and the effect of an electric field. The results showed that ferromagnetism/anti-ferromagnetism can be achieved when nitrogen dopant atoms are arranged in a chain-like manner, and that a strong transversal electric field can induce magnetization in ACNT:N. The study is of great significance for spintronics and gas-sensing devices.