Petrucio Barrozo

Ferromagnetism in Mn half-doped LaCrO3 perovskite

In this work, we present results on the structural, electrical, and magnetic properties of pure and half-doped LaCrO3 compounds. It is observed that including Mn the lattice structure changes from orthorhombic to rhombohedral. The electrical transport in LaCrO3 can be described by a band gap model, whereas in La2CrMnO6, a charge localization occurs and the electrical transport is described by a variable range hopping model. The magnetic measurements show that LaCrO3 is a G-type antiferromagnetic with a Neel temperature at 290 K, and the Mn doping favors the ferromagnetic order and reduces the transition temperature.

Superconducting properties of Nb/Pb/Nb trilayer

Fabrication of superconducting layered systems offers fascinating possibilities to observe novel superconducting phenomena. In this work we study a new nanostructured superconducting trilayer. Nb/Pb/Nb trilayer was grown by magnetron sputtering and the superconducting properties were studied via magnetic and electrical transport measurements. The magnetization and resistivity have been analyzed as functions of the temperature and magnetic field applied perpendicularly to the layers. The sample presents sharp resistive and magnetic transitions at TC = 7.2 K. Vortex avalanches attributed to thermomagnetic instabilities were observed in magnetization versus applied field loops. The temperature dependence of μ0Hc2 presents a positive upward curvature at low temperatures, indicating a crossover which is consistent with the Takahashi–Tachiki model for superconducting superlattices. The temperature dependence of the lower critical field μ0Hc1(T) presents an unconventional feature consistent with a multicomponent behavior with spatially separated components.