RESUMO
Here, using various substrates, we demonstrate that the in-plane uniaxial strain engineering can enhance the Jahn-Teller distortions and promote selective orbital occupancy to induce an emergent antiferromagnetic insulating (AFI) phase at x = 1/3 of La1-xCaxMnO3. Such an AFI phase depends not only on the magnitude of epitaxial strain but also on the symmetry of the substrates. Using the large uniaxial strain imparted by DyScO3(001) substrate, the AFI ground state is achieved in a wide range of doping levels (0 ≤ x ≤ 1/2), leaving an extended AFI phase diagram. Moreover, it is found that hydrostatic pressure can tune the AFI phase back to a hidden ferromagnetic metallic phase, accompanied by the formation of accommodation strain. The coaction of the accommodation strain, uniaxial strain, and hydrostatic pressure produces complex phase competition and evolution, and the result may shed light on phase space control of other functional perovskites with the competing magnetic interactions.
RESUMO
In transition-metal-oxide heterostructures, the anomalous Hall effect (AHE) is a powerful tool for detecting the magnetic state and revealing intriguing interfacial magnetic orderings. However, achieving a larger AHE at room temperature in oxide heterostructures is still challenging due to the dilemma of mutually strong spin-orbit coupling and magnetic exchange interactions. Here, Ru-doping-enhanced AHE in La2/3 Sr1/3 Mn1-x Rux O3 epitaxial films is exploited. As the B-site Ru doping level increases up to 20%, the anomalous Hall resistivity at room temperature can be enhanced from nΩ cm to µΩ cm scale. Ru doping leads to strong competition between the ferromagnetic double-exchange interaction and the antiferromagnetic superexchange interaction. The resultant spin frustration and spin-glass state facilitate a strong skew-scattering process, thus significantly enhancing the extrinsic AHE. The findings can pave a feasible approach for boosting the controllability and reliability of oxide-based spintronic devices.
RESUMO
In this study, hexagonal-packed Si nanorods (SiNRs) arrays were fabricated and conjugated with Au nanoparticles (AuNPs) in different spatial distributions for surface-enhanced Raman spectroscopy (SERS). The AuNPs were functionalized on the bottom of SiNRs (B-SiNRs@AuNPs), top of SiNRs (T-SiNRs@AuNPs) and sides of SiNRs (S-SiNRs@AuNPs), respectively. Our results demonstrated that the SiNRs conjugated with AuNPs on the sides achieved high reproducibility in detection of R6G molecules, while the AuNPs on the top of the SiNRs obtained the strongest Raman enhancement. In addition, the substrate with S-SiNRs@AuNPs obtained the highest spatial uniformity of enhancement. The finite-difference time-domain simulation gave further evidence that the incident light could be confined in the space of SiNRs arrays and yield a zero-gap enhancement coupled with the AuNPs. Our study provided a spatially tunable SiNRs@AuNPs substrate with high sensitivity and reproducibility in molecular detection.