Critical behavior study of the spin ordering transition in RVO3 (R = Ce, Pr, Nd, Sm, Gd, Er) by means of ac photopyroelectric calorimetry

The thermal diffusivity of RVO3 single crystals (R = Ce, Pr, Nd, Sm, Gd, and Er) has been measured with an ac photopyroelectric calorimetry in the region in which the G-type orbital ordering and C-type spin ordering take place. Detailed measurements in the close neighbourhood of the spin ordering temperature have allowed to extract the critical parameter α and the critical ratio A+/A− for this transition. While the samples containing Ce, Nd, Sm and Er belong to the 3D-XY universality class (showing that the spins have an easy plane anisotropy), the sample with Gd, which is known to present a clear easy axis, belongs to the 3D-Ising class. Finally, PrVO3 shows an effective isotropic behavior, as the critical parameters found agree with the 3D-Heisenberg class

Reusable Au/Pd-coated chestnut-like copper oxide SERS substrates with ultra-fast self-recovery

Reliable and reusable plasmonic substrates are crucial for the development of biosensing applications using surface-enhanced Raman scattering (SERS), as they can provide unique advantages for ultrafast and accurate single-molecule recognition of different species. These properties are unrevealed in this paper, where thermally annealed cupric CuO and cuprous oxide Cu2O heterostructures were used as templates for highly stable nanotextured surfaces and design of robust 3D plasmonic biochips. Differently tailored nano/micro-roughness provided outstanding light trapping abilities that lead to significant SERS performance improvement. It was found that Cu2O chestnut-like substrate activated with 80 nm Au/Pd alloy film reveals impressive 3.7-fold Raman signal increment in respect to grainy-like structure and about twice larger amplification than that of nanowires enriched platform decorated in the same manner. Large enhancement factor AEF ~5 × 105 of a chestnut-like Au/Pd@/Cu2O chip allows adding it up to the list of the most effective oxide-based plasmonic substrates. Moreover, the substrate shows unprecedented durability during repetitive plasma-cleaning, demonstrating a remarkable 100 self-recovery in less than 1 min, accompanied by virtually no thickness degradation of the plasmonic layer. © 2020 Elsevier B.V