Ferromagnetic insulating and spin glass properties of La0.7Sr0.3MnO3–TiO2 composites

Abstract In this study, the effect of TiO 2 doping on the electro-magnetic properties of (1− x )La 0.7 Sr 0.3 MnO 3 + x TiO 2 (with 0%≤ x ≤6%, in wt%) composites has been investigated. X-ray diffraction observations show the evidence of reaction between the La 0.7 Sr 0.3 MnO 3 and TiO 2 grains. Also the results show that by increasing TiO 2 doping levels, the metal insulator transition temperatures decrease and the system becomes an insulator. Furthermore, the paramagnetic–ferromagnetic transition temperature also decreases as TiO 2 content increases. The spin glass state exists in the composites with x =5% and 6%. The dynamic properties of the magnetic properties are investigated by temperature dependence of dc magnetization and frequency dependence of ac susceptibilities. A dynamic scaling analysis of ac susceptibility data using conventional critical slowing down indicates that a finite spin-glass phase-transition temperature ( T g ) and a dynamic exponent ( zv ) change from 103 K and 9.30 correspondingly for 0.95La 0.7 Sr 0.3 MnO 3 /0.05TiO 2 to 133 K and 9.10, for 0.94La 0.7 Sr 0.3 MnO 3 /0.06TiO 2 . In addition, MR in low temperature of these samples decline simultaneously with occur spin-glass behavior. These results are interpreted as the dilution of Mn 3+ /Mn 4+ interactions by the random Ti substitution on the Mn site considerably reduces the ferromagnetic double exchange interaction within the manganese lattice.