Electron magnetic resonance studies of nanomanganite Nd0.67Sr0.33MnO3

TL;DR

This study investigates how particle size affects magnetic, transport, and electron magnetic resonance properties of Nd0.67Sr0.33MnO3 nanoparticles, revealing size-dependent magnetic transitions and core-shell magnetic behavior.

Contribution

It provides new insights into the size-dependent magnetic and EMR spectral properties of Nd0.67Sr0.33MnO3 nanoparticles, including core-shell structure estimation.

Findings

Ferromagnetic to paramagnetic transition temperature decreases with particle size.

EMR spectra show distinct behaviors below and above Tc, indicating ferromagnetic and paramagnetic phases.

Shell thickness of nanoparticles estimated at 0.7-1 nm from EMR data.

Abstract

Nd_0.67Sr_0.33MnO_3 nanoparticles with the grain size of about 30 nm are prepared by sol-gel method.These nanopowders are annealed at four different temperatures viz. 800 oC, 900 oC, 1000 oC and 1100 oC to study the effect of particle size on magnetic, transport and electron magnetic resonance (EMR) spectral parameters. The samples are characterized by XRD, SEM, EDAX and TEM. The ac susceptibility experiments show that as the particle size increases the ferromagnetic to paramagnetic transition temperature (Tc) decreases. The metal-insulator transition temperature also changes with the particle size as revealed by resistivity measurements. EMR spectra of the nanopowders are recorded from room temperature down to 4K using an X-band EPR spectrometer. the spectra could be fitted using two broad-Gaussian lineshapes below Tc and suggested the ferromagnetic nature of the samples. Above Tc a single Lorenzian fits the signals as expetced for paramagnetic samples. The EMR spectral parameters are found to be different from the bulk (polycrystalline)sample data. The spectral parameters show variation with the particle size. The presence of the two signals in the ferromagnetic phase is attributed to core and shell regions in the nanoparticles. We could estimate the shell thickness from the EMR intensity data as 0.7 - 1 nm which agrees with other measurements.