Abstract
Polymer-assisted deposition method has been used to fabricate self-assembled epitaxial La0.67Ca0.33MnO3:NiO and La0.67Ca0.33MnO3:Co3O4 films on LaAlO3 substrates. Compared to pulsed-laser deposition method, polymer-assisted deposition provides a simpler and lower-cost approach to self-assembled composite films with enhanced low-field magnetoresistance effect. After the addition of NiO or Co3O4, triangular NiO and tetrahedral Co3O4 nanoparticles remain on the surface of La0.67Ca0.33MnO3 films. This results in a dramatic increase in resistivity of the films from 0.0061 Ω•cm to 0.59 Ω•cm and 1.07 Ω•cm, and a decrease in metal-insulator transition temperature from 270 K to 180 K and 172 K by the addition of 10%-NiO and 10%-Co3O4, respectively. Accordingly, the maximum absolute magnetoresistance value is improved from −44.6% to −59.1% and −52.7% by the addition of 10%-NiO and 10%-Co3O4, respectively. The enhanced low-field magnetoresistance property is ascribed to the introduced insulating phase at the grain boundaries. The magnetism is found to be more suppressed for the La0.67Ca0.33MnO3:Co3O4 composite films than the La0.67Ca0.33MnO3:NiO films, which can be attributed to the antiferromagnetic properties of the Co3O4 phase. The solution-processed composite films show enhanced low-field magnetoresistance effect which are crucial in practical applications. We expect our polymer-assisted deposited films paving the pathway in the field of hole-doped perovskites with their intrinsic colossal magnetoresistance.
Highlights
The discovery of intrinsic colossal magnetoresistance (MR) in hole-doped perovskites with a formula, La1−xAx MnO3 (A =Ca, Sr, and Ba) has established their potential applications in memory devices and magnetic sensors[1,2,3,4,5,6,7]
−2 5% of MR at 93 K under 1.15 T was observed in LCMO:15% V2O5 composite fabricated by a two-step solid-state reaction[22] and a pronounced low-field magnetoresistance (LFMR) of −23.9% at 10 K in a field of 0.5 T was achieved in LSMO:ZnO (LSMO: La0.67Sr0.33MnO3) composite film[14]
A tunable and enhanced LFMR of −3 0% at 154 K under 0.1 T was observed in a LSMO:ZnO nanocomposite film grown by pulsed-laser deposition (PLD)
Summary
The discovery of intrinsic colossal magnetoresistance (MR) in hole-doped perovskites with a formula, La1−xAx MnO3 (A =Ca, Sr, and Ba) has established their potential applications in memory devices and magnetic sensors[1,2,3,4,5,6,7]. A tunable and enhanced LFMR of −3 0% at 154 K under 0.1 T was observed in a LSMO:ZnO nanocomposite film grown by pulsed-laser deposition (PLD) Most of these reported composite films were, prepared by either complicated multiple-steps or costly high-vacuum processes. We report self-assembled LCMO:NiO and LCMO:Co3O4 composite films epitaxially grown by polymer-assisted deposition (PAD) technique which demonstrate enhanced LFMR. Under a magnetic field of 3 T, MR values of −44.6% at 255 K for LCMO, −59.1% at 180 K for LCMO:10%-NiO, and −52.7% at 172 K for LCMO:10%-Co3O4 were achieved, respectively This revealed that the composite films possess high LFMR and their effect was enhanced even further with the addition of 10%-NiO or 10%-Co3O4 insulating phases of the grain boundaries
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