Influence of Fe in giant magnetoresistance ratio and magnetic properties of La[sub 0.7]Ca[sub 0.3]Mn[sub 1−x]Fe[sub x]O[sub 3] perovskite type compounds

In this work polycrystalline perovskite with composition La0.7Ca0.3Fe0.05Mn0.95O3 has been produced by standard ceramic method. A considerable change occurs in magnetic, transport and magnetoresistance properties with respect to the classic composition without Fe. The introduction of a different metal, Fe, in Mn-O layer causes a decrease of about 50 K in the value of T-C. In the same way, a decrease of about 10-15% in the average magnetic moment measured at 1 T is also observed. On the other hand, the introduction of Fe does not cause any appreciable change in the value of the lattice parameter. This new compound presents 60% of giant magnetoresistance ratio at 200 K. Magnetization vs. temperature 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 ferromagnetic one. A qualitative discussion of the effect in the magnetic and transport properties of these compounds, caused by the substitution of some Mn atoms by Fe is given.