Combined strain and high-pressure oxygen treatment effects and phase separation in La0.67Ca0.33MnO3 thin films

Evidence for phase separation in high-pressure oxygen-treated La0.67Ca0.33M nO3/(100)MgO thin films is presented. This phase-separated state is not obs erved for the x = 0.33 classical doping level either for bulk material or f or as-prepared thin films. It originates from the combined influence of two factors: large strains due to the film-substrate lattice mismatch and high -pressure (100 bar) annealing in oxygen. These factors weaken double exchan ge, drastically enhance low-field magnetoresistance, and lead to hysteresis phenomena. The experimental results are interpreted in terms of phase sepa ration of the film volume into the ferromagnetic conductive matrix with inc lusions of spin-glass-like clusters. (C) 2001 MAIK "Nauka / Interperiodica" .