119Sn NMR probe of magnetic fluctuations in SnO2 nanoparticles

TL;DR

This study uses 119Sn NMR to investigate magnetic fluctuations in SnO2 nanoparticles, revealing surface defect-induced magnetism and distinct relaxation behaviors compared to bulk material.

Contribution

It demonstrates the presence of magnetic fluctuations in SnO2 nanoparticles through NMR, highlighting differences from bulk properties and suggesting surface defects as the source.

Findings

15% loss of NMR signal in nanoparticles indicating ferromagnetism

Stretched exponential recovery of nuclear magnetization in nanoparticles

Higher 119Sn 1/T1 at room temperature in nanoparticles

Abstract

119Sn nuclear magnetic resonance (NMR) spectra and spin-lattice relaxation rate (1/T1) in SnO2 nanoparticles were measured as a function of temperature and compared with those of SnO2 bulk sample. A 15% loss of 119Sn NMR signal intensity for the nano sample compared to the bulk sample was observed. This is indicative of ferromagnetism from a small fraction of the sample. Another major finding is that the recovery of the 119Sn longitudinal nuclear magnetization in the nano sample follows a stretched exponential behavior, as opposed to that in bulk which is exponential. Further, the 119Sn 1/T1 at room temperature is found to be much higher for the nano sample than for its bulk counterpart. These results indicate the presence of magnetic fluctuations in SnO2 nanoparticles in contrast to the bulk (non-nano) which is diamagnetic. These local moments could arise from surface defects in the nanoparticles.