INFLUENCE OF FE IN GIANT MAGNETORESISTANCE RATIO AND MAGNETIC-PROPERTIES OF LA0.7CA0.3MN1-XFEXO3 PEROVSKITE-TYPE COMPOUNDS

In this work polycrystalline perovskite with composition La0.7Ca0.3Fe0 .05Mn0.95O3 has been produced by standard ceramic method. A considerab le change occurs in magnetic, transport and magnetoresistance properti es with respect to the classic composition without Fe. The introductio n of a different metal, Fe, in Mn-O layer causes a decrease of about 5 0 K in the value of T-C. In the same way, a decrease of about 10-15% i n the average magnetic moment measured at 1 T is also observed. On the other hand, the introduction of Fe does not cause any appreciable cha nge in the value of the lattice parameter. This new compound presents 60% of giant magnetoresistance ratio at 200 K. Magnetization vs. tempe rature measurements in zero field cooling and field cooling show clear differences at applied fields below 80 km(-1). Such a behavior, also observed in La0.7Ca0.3MnO3 sample, is not recognizable as a simple fer romagnetic one. A qualitative discussion of the effect in the magnetic and transport properties of these compounds, caused by the substituti on of some Mn atoms by Fe is given. (C) 1997 American Institute of Phy sics.