Enhanced Low-field Magnetoresistance of La_0.7Sr_0.3Mn_1+dO₃-Mn₃O₄Composite Films Prepared by ex-situ Solid Phase Crystallization

We report improved low-field magnetoresistance (LFMR) effects of the La 0.7 Sr 0.3 Mn 1+d O 3- Mn 3 O 4 composite films with the nominal composition of La 0.7 Sr 0.3 MnO 3 (LSMO)-50 mol% Mn 3 O 4 . The composite films were fabricated by ex-situ solid phase crystallization (SPC) of amorphous films at the annealing temperature region of 900-1100℃ for 2 h in a pure oxygen atmosphere. The amorphous films were deposited on polycrystalline BaZrO 3 (poly-BZO) substrates by dc-magnetron sputtering at room temperature. The Curie temperatures (TC) of all composite films were insignificantly altered in the range of 368-372 K. The highest LFMR value of 1.29 % in 0.5 kOe with the maximum dMR/dH value of 37.4%kOe ?1 at 300 K was obtained from 900 nm-thick composite film annealed at 1100℃. The improved LFMR properties of the composite films are attributed to effective spin-dependent scattering at the La 0.7 Sr 0.3 Mn 1+d O 3 grain boundaries sharpened by adjacent chemically compatible Mn 3 O 4 grains.