Abstract
Pr0.5Sr0.5MnO3 (PSMO) thin film is epitaxially grown on (001)-oriented LaAlO3 single-crystal substrate using pulsed laser deposition (PLD). It is found that the as-grown PSMO film shows compressive strain in plane and tensile strain out of the plane. Upon annealing at 900°C in the air, the strain is significantly relaxed. The paramagnetic to ferromagnetic phase transition temperature TC shifts from 200 K to 220 K, and the antiferromagnetic insulating phase is suppressed in the phase separated state at low temperature. In addition, the magnetoresistance (MR) is found to increase around the ferromagnetic transition temperature, whereas it decreases from 99% to 60% at low temperature of 20 K.
Highlights
Substrate and PSMO suggests the epitaxial film is subjected to a compressive strain in plane
To distinguish strain effect from the change of oxygen deficiency induced by the annealing, we studied the influence of annealing on PSMO thin film deposited on (001)-oriented (LaAlO3)0.3–(SrAl0.5Ta0.5O3)0.7(LSAT) substrates with identical conditions
Two types of MR phenomena in various manganite materials have been revealed: (i) at the Curie temperature region, a somewhat ‘standard’ MR1 effect takes place since small field can align the moments of the ferromagnetic islands of random orientation, leading to a percolative conductor; (ii) at low temperatures where the system is insulating, a huge MR is detected as well. Such MR2 originates from the competition between ferromagnetic metallic (FMM) phase and antiferromagnetic insulating (AFI) phase.[20]. These two types of MR phenomena are both found in the as-grown PSMO film upon cooling
Summary
The FMM-AFI phase transition is observed in the greatly strained (001)-oriented films and the transition temperature decreases with increasing thickness due to strain relaxation.[14,15,16] In order to obtain strained epitaxial (001)-oriented PSMO film on LAO substrate, the growth temperature should be higher than 700◦C. The effect of annealing on the PSMO film grown on the (001)-oriented LAO single-crystal substrate is thoroughly investigated.
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