Enhancement of Low-field Magnetoresistance in Self-Assembled Epitaxial La0.67Ca0.33MnO3:NiO and La0.67Ca0.33MnO3:Co3O4 Composite Films via Polymer-Assisted Deposition

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.

Synthesis and Characterization of Vertically Aligned La0.7Sr0.3MnO3:NiO Nanocomposite Thin Films for Spintronic Applications

“…Therefore, composite thin films LA14 (dense nanomaze, ε = 0.72%) and ST14 (nano columnar, ε = 0.85%) lose their metallic conductivities and show a huge (few orders of magnitude higher) enhancement in the resistivity and semiconducting behavior without any metal–insulator transition (Figure b). The enhancement in the resistivity and the low-temperature upturn can be attributed to the presence of the highly resistive NiO phase boundaries with a large number of grains and increased disorder. , This highly resistive NiO phase obstructs the spin alignment and increases the tunneling barrier height between the neighboring magnetic grains . It should be noted that when the magnetic field 80 kOe is applied, the M–I transition of LSMO phase increases to 280 K in LA25 sample, whereas in LA7 sample, the M–I transition enhances to 265 K. Interestingly, even in the LA14 sample, which displays semiconducting behavior at all temperatures, a huge change in resistivity under the application of a magnetic field is observed, which is suggestive of a tunneling type of conduction between LSMO grains via insulating NiO grains.…”

“…35,36 This highly resistive NiO phase obstructs the spin alignment and increases the tunneling barrier height between the neighboring magnetic grains. 50 It should be noted that when the magnetic field 80 kOe is applied, the M−I transition of LSMO phase increases to 280 K in LA25 sample, whereas in LA7 sample, the M−I transition enhances to 265 K. Interestingly, even in the LA14 sample, which displays semiconducting behavior at all temperatures, a huge change in resistivity under the application of a magnetic field is observed, which is suggestive of a tunneling type of conduction between LSMO grains via insulating NiO grains. The temperature-dependent magnetoresistance MR % = [R T (H) − R T (0)/R T (0)] × 100 is shown in Figures 6a−c under an applied field of 0 and 80 kOe.…”

Enhancement of the Magnetotransport Behavior in a Phase-Separated LaAgCaMnO3 Polycrystalline: Unraveling the Role of a Multi-Double-Exchange Mechanism

“…In both processes, the MR curves exhibits a plateau-like shape at low-temperature region (i.e., around the T ρ ) and the MR value was recorded to be 99% for an applied field of 2 T. Similar and lower obtained MR values have also been presented in previous studies on manganese oxides (Table ). ,− With an applied field of 5 T, the maximum MR value is ∼100 and 94.68% around 116 and 173 K for cooling and heating, respectively. For an applied field of 8 T, the maximum MR value is ∼100 and 95% at 117 and 178 K for cooling and heating, respectively.…”

Exchange Bias Effect along Vertical Interfaces in La0.7Sr0.3MnO3:NiO Vertically Aligned Nanocomposite Thin Films Integrated on Silicon Substrates

“…VAN nanostructure design provides a significant amount of vertical interface area depending on the pillar size and density. , Because of the versatile combination of oxide–oxide multifunctional thin film systems and the strong coupling of the two phases and the heterointerface effect, unique properties have been obtained beyond exchange bias along vertical interfaces, such as multiferroic, , magnetoresistance, − enhanced flux pinning for superconductors, − and enhanced ionic conductivity in electrolytes for solid oxide fuel cells (SOFC). , Integrating many of these multifunctional VAN systems on silicon substrates could lead to practical applications of these new materials. Thus, the successful demonstration of Si integration for the VANs with the EB effect and MR property is not only critical for spintronic and magnetic storage applications, but also has broader impacts on other multifunctional VAN systems and their future applications.…”