INFLUENCE OF GRAIN SIZE ON MAGNETOCALORIC EFFECT IN THE NANOCRYSTALLINELa0.8Te0.2MnO3

Abstract

The nanocrystalline La0.8Te0.2MnO3samples are prepared by sol-gel method and show rhombohedral crystal structure with R3c space group at room temperature. The calculated crystallite sizes are ~55 nm, 40 nm and 25 nm for calcined at 700°C, 800°C and 900°C temperatures. The SEM images show the grain size increases as the calcination temperature increases and the values are in good agreement with that obtained from X-ray diffraction analysis. The samples undergo paramagnetic to ferromagnetic transition and follow Curie–Weiss law in the paramagnetic region. The maximum entropy change are ~3.2 J kg-1K-1, 3 J kg-1K-1and 2 J kg-1K-1for a field change of 20 kOe for 55 nm, 40 nm and 25 nm samples respectively. In the framework of Landau theory of phase transition, the experimentally observed magnetic entropy change and theoretical predicted model fits well for all the nanoparticles.