Grain Size Effect on the Magnetic Properties of Sm0.08Ca0.92MnO3 Manganite

Abstract Here we present a comparative study of the temperature dependent magnetic properties of nanosized and bulk samples of Sm 0.08 Ca 0.92 MnO 3 (SCMO) manganite. Nanoparticles of SCMO (mean diameter ∼ 27, 22 and 16 nm) were synthesized by sol-gel technique and the bulk samples were obtained by sintering the nanoparticles at high temperatures. The samples were characterized by X-ray powder diffraction, energy dispersive X-ray analysis and transmission electron microscopy. The magnetic properties were studied by SQUID magnetometer and Electron magnetic resonance (EMR) spectroscopy. Temperature dependence of dc-magnetization showed that the nanoparticles underwent ferromagnetic transition at 103 K where as the bulk sample showed the same at 105 K. The field cooled curve shows that the magnetization decreases with the size reduction. The EMR studies substantiate the presence of ferromagnetism in the bulk sample as well as in nanosamples but with a weakened strength in nanosamples. In manganites linewidth shows a characteristic minimum near 1.1 T C where T C is the FM transition temperature. We observe this minimum becomes less shallow as the size decreases. The behaviour of the nanoparticles is ascribed to core shell model; reduction of magnetization in the nanoparticles is due to uncompensated surface spin.