Size-induced Griffiths phase-like in ferromagnetic metallic La0.67Sr0.33MnO3 nanoparticles

Abstract

The La0.67Sr0.33MnO3 (LSMO) compound was prepared by the citrate-gel method and annealed at different temperatures (600°C (L6), 800°C (L8), 1000°C (L10) and 1200°C (L12)). X-ray diffraction (XRD), transmission electron microscopy (TEM) and magnetic measurements were used to investigate the particle size effects on the physical properties. All samples were found to be single phase crystallizing in rhombohedral symmetry with R3¯c space group. It was also found that the reduction of grain size intensively affects the magnetic properties of these compounds. The variation in the magnetic properties as a function of the particle size may be explained in terms of core–shell model. For the L6, L8 and L10 samples, the weaker effective magnetic moments and the deviation of the inverse susceptibility from the Curie–Weiss law were observed, indicating the possible existence of a Griffiths-like cluster phase. However, the latter was found to disappear for L12. The reduction of Griffiths phase may be related to the weaker FM interactions which were weakened by the size reduction, possibly due to the surface spin disorders. Otherwise, the competition between paramagnetic and ferromagnetic phases may strongly affect the magnetic properties that may result in the disappearance of the Griffiths phase.