¹¹⁹Sn NMR probe of magnetic fluctuations in SnO₂ nanoparticles

¹ Department of Physics, Indian Institute of Technology Bombay - Powai, Mumbai 400076, India
² Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR) - Jakkur P. O., Bangalore 560064, India

^a tusdey@gmail.com

Received: 29 August 2011
Accepted: 2 November 2011

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.