Low Field Magnetoresistance Properties of (La_(0.75)Sr_(0.25))_(1.05)Mn_(0.95)O_3 Poly crystalline Thin Films on a-SiO_2/Si Substrates Prepared by ex-situ Solid Phase Crystallization

摘要

We report the low field magnetoresistance (LFMR) properties of (La_(0.75)Sr_(0.25))_(1.05)Mn_(0.95)O_3(LSMO) films on a-SiO_2/Si substrates, prepared by ex-situ solid phase crystallization of amorphous films deposited by dc-mag-netron 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-SiO_2 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.