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Electron magnetic resonance studies of nanomanganite $Nd_0_._6_7Sr_0_._3_3MnO_3$

Rao, SS and Sarangi, Subhasis and Venkataiah, G and Reddy, Venu Gopala and Bhat, SV (2005) Electron magnetic resonance studies of nanomanganite $Nd_0_._6_7Sr_0_._3_3MnO_3$. [Preprint]

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Abstract

$Nd_0_._6_7Sr_0_._3_3MnO_3$ (NSMO) nano particles with the grain size of about 30 nm are prepared by sol-gel method. These nanopowders are annealed at four different temperatures viz 800 $^\circ C$, 900$^\circ C$, 1000$^\circ C$ and 1100$^\circ C$ to study the effect of particle size on magnetic, transport and electron magnetic resonance spectral parameters. The samples are characterized by XRD, SEM, EDAX and TEM. The a.c susceptibility experiments show that as the particle size increases the ferromagnetic to paramagnetic transition temperature $(T_c)$ decreases. The metal-insulator transition temperature also changes with the particles size as revealed by resistivity measurements. Electron magnetic resonance (EMR) spectra of the nano powders are recorded from room temperature down to 4K using an X- band ESR spectrometer. EMR spectra could be fitted using two broad-Gaussian lineshapes below $T_c$ and suggested the ferromagnetic nature of the sample.Above Tc a single Lorentzian fits the signals as expected for a paramagnetic sample. 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 of the nano particles. We could estimate the shell thickness from the EMR intensity data as 0.7-1nm which agrees well with the other measurements.

Item Type: Preprint
Department/Centre: Division of Physical & Mathematical Sciences > Physics
Date Deposited: 09 Jan 2006
Last Modified: 19 Sep 2010 04:22
URI: http://eprints.iisc.ernet.in/id/eprint/4872

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