Study of the magnetoresistive properties of (La1.6Dy0.2Sr1.2)Mn2-xNix/FexO7 perovskite manganites

Abstract

Polycrystalline samples (La, ~DYU1SrLl)Mnl_,Ni,fFe,D-r (with )\=0.0,0.1,0.2) were prepared using the oonventional solid-state reaction technique and sintered at temperature llOOue for 24 hours in air. Phase purity and structure were checked by powder X-ray diffraction (XRD) using the MoKu radiation (J...= 0.710689 A).For thc structure determination, dilfraction patterns were recorded in the 26 range from 100to 70o.The IX: electrical resistivity for various polycrystalline samples was measured from room temperature down to liquid nitrogen temperature both at zero field and at applied magnetic field of 0.7T using four probe method. In the present investigation it is observed that all the samples showed metal insulator (M-I) transition with a peck in the electrical resistivity around M-I transition temperature Tp• With the increase ofNi or Fe doping the resistivity increases but M-I transition temperature Tp decreases. M-I transition temperature Tp also inl,,-nlao;edin presence of O.7T magnetic field. Magnetoresistance (MR) measurements were carried out in a magnetic field ofO.7T in the temperature range of77K to 300K, The MR behaviour was discussed a~ a function of magnetic field both at room temperature and at liquid nitrogen temperature. Room temperature MR is found to be very low, almost 0.110/••..1..69% and is almost linear with field. A large value ofMR is observed at 78K in the presence of low applied magnetic field. The higher percentage of Fe and Ni in these compounds enhances paramagnetic insulating phase. The plot of In(plPol vs r' curve means that the conduction occurred tluough a thennaIly activated pl'OCe5Sabove the transition temperature.