Low field magnetoresistance properties of (La0.75Sr0.25)1.05Mn0.95O3 polycrystalline thin films on a-SiO2/Si substrates prepared by ex-situ solid phase crystallization

We report the low field magnetoresistance (LFMR) properties of (La_0.75Sr_0.25)_1.05Mn_0.95O₃(LSMO) films on a-SiO₂/Si substrates, prepared by ex-situ solid phase crystallization of amorphous films deposited by dc-magnetron sputtering at room temperature. The average grain size of the LSMO films was gradually increased with increasing annealing temperature (T _an ) and film thickness. High T _an also caused the growth of an amorphous inter-diffusion layer between a-SiO₂ and LSMO. The highest LFMR values of 16 and 1.0 % were achieved at 100 K, 1.2 kOe and 300 K, 0.5 kOe, respectively, from an LSMO film of 200 nm thickness annealed at 900 °C. In accordance with a modified brick layer model, grain boundary areal resistance gradually increased with increasing T _an and decreasing film thickness due to the penetration of the amorphous inter-diffused phase into the LSMO grain boundary. Improved LFMR values are attributable to modification of the LSMO grain boundary into a more effective spin-dependent scattering center.