Indirect Exchange Interaction in Fully Metal-Semiconductor Separated SWCNTs Revealed by ESR

TL;DR

This study investigates the ESR response of metal-semiconductor separated SWCNTs, revealing temperature-dependent spin interactions, a ferromagnetic transition below 10 K, and the role of RKKY and Orbach processes in spin dynamics.

Contribution

It demonstrates the distinct ESR behaviors of metal and semiconductor SWCNTs and identifies the mechanisms behind their spin interactions and relaxation processes.

Findings

Metal tubes show larger ESR line width decreasing with temperature.

Semiconductor tubes exhibit increasing line width with temperature.

A ferromagnetic phase transition occurs below 10 K.

Abstract

The ESR response from highly metal-semiconductor(M-SC) separated SWCNTs for temperatures T between 0.39 and 200 K is characteristically different for the two systems. The signal originates from defect spins but interaction with free electrons leads to a larger line width for M tubes. The latter decreases with increasing T whereas it increases with T for SC tubes. The spins undergo a ferromagnetic phase transition below around 10 K. Indirect exchange is suggested to be responsible for the spin-spin interaction, supported by RKKY interaction in the case of M tubes. For SC tubes spin-lattice relaxation via an Orbach process is suggested to determine the line width.