Enhanced low-field magnetoresistance in La _0.67Sr _0.33MnO ₃:MgO composite films

In this paper, we report low-field magnetoresistance observed in preferentially c-axis oriented La _0.67 Sr _0.33MnO ₃:MgO composite films fabricated on (001) LaAlO ₃ substrates using a hybrid solution route. Addition of MgO in the composite film results in lowering of Curie temperature (∼300 K) from that of the pure film (∼360 K). The resistivity increases and temperature of highest resistivity of the composite films decrease with the addition of MgO. This behavior is attributed to a small substitution of Mg ² in the manganite lattice and the presence of MgO near the manganite grain boundaries, thus building tunneling barriers and enhancing the spin polarized tunneling in the composite films. The values of low-field magnetoresistance increase with MgO addition and the composite film with highest amount of MgO exhibits maximum MR of -33 at 0.5 T (5000 Oe) and 10 K.