STRUCTURAL, MAGNETIC AND MAGNETOTRANSPORT BEHAVIOUR OF (Pro.7Sro.3MnO3)1-x (NiO)x AND Sr2-xEuxFeM006

Abstract

We have synthesized (Pro.7Sr0.3MnO3)1-x/NiOx (x = 0, 5%, 10%, 15% and 20%) composites through a Sol- gel route and have characterized them for Structural, magnetic and magnetotransport properties. The structure and morphology of the composites have been studied by the X-ray diffraction (XRD) and field emission scanning electronic microscopy (FESEM). The XRD and FESEM results indicate that no reaction occurs between PSMO and NiO grains, and that NiO segregates mostly at the grain boundaries of PSMO. The magnetic properties reveal that the ferromagnetic order of PSMO is weakened by addition of NiO. The results also show that NiO has a direct effect on the resistance of PSMO / NiO composites, especially on the low-temperature resistance. With increase of the NiO doping level, Tp shifts to a lower temperature and the resistance increases. In the present work, it is suggested that the large MR at low temperature (below 140 K) is low field magnetoresistance (LFMR) caused by spin polarized tunneling, whereas at around room temperature it is caused by magnetic disordering. The crystalline structure; grain morphology, electrical and magnetic properties of Sr2_XEuFeMoO6 (0 ( x <l) double perovskite has been investigated by means of X-ray powder diffraction, FESEM, R-T measurement and SQUID. The XRD pattern indicates that all the samples are of single phase. Due to the smaller ionic radius of Eu than that of Sr2+ ions, the lattice constants and unit cell volume of the compound decrease slightly with x. Resistivities show a semiconducting behavior for all samples and increase with x. The magneto-resistance (MR) of the compound with x =1.0 is higher than that of the other samples. The saturation magnetic moment decreases with increases the Eu. content. Parent compound Sr2FeMo06 exhibits saturation magnetic moment value of 30.16 & 16.26 at 10K and 300K in a magnetic field of 70kOe respectively.