Observation of spin-phonon coupling in GdCl3 filled carbon nanotubes

TL;DR

This study demonstrates enhanced spin-phonon coupling in gadolinium-filled carbon nanotubes, revealing a superparamagnetic phase transition below 100 K and phonon hardening near the transition, indicating strong spin-phonon interactions.

Contribution

It provides experimental evidence of enhanced spin-phonon coupling in GdCl3-filled carbon nanotubes using magnetometry and Raman spectroscopy, highlighting a phase transition and phonon behavior.

Findings

Superparamagnetic phase transition below 100 K

Phonon hardening near 47 K

Resonance between phonon mode and spin flip frequency

Abstract

The enhancement of spin-phonon coupling in gadolinium filled double walled carbon nanotubes (GdCl3@DWNTs) is demonstrated through temperature dependent magnetrometry and polarized Raman Spectroscopy (PRS). Temperature dependent susceptibility measurements show that the GdCl3@DWNTs undergo a superparamagnetic phase transion at temperatures below 100 K with a blocking temperature at approximately 47 K. From the temperature dependent PRS, it is observed that a distinct phonon hardening occurs for the G-band modes at temperatures close to the onset of the superparamagentic phase. This is in contract to pristine DWNTs where phonon modes saturates to a constant frequency at low temperatures. The abrupt increase in phonon frequency is indicative of a pronounced spin-phonon coupling. The enhanced coupling in the GdCl3@DWNTs is believed to occur due to resonance between nanotube phonon mode and spin flip frequency as temperature decreases.