Erivaldo Montarroyos

Probing a resonant circuit with a PC sound card

We discuss an inexpensive experimental system that enables us to generate and acquire electronic signals using only a personal computer and its sound card to study the resonance of an RLC oscillator circuit.

Decodificando o Controle Remoto com a Placa de Som do PC

In this work we analyzed the decoding of the TV remote control using a PC sound card. The infrared coded signal is received by an optical sensor and is sent to the line-in channel of the PC sound card, which is used as an analogical-digital converter (A/D) of low cost and high efficiency for low frequency AC signals. A didactic software was used to simulate in the computer a virtual scope, allowing to observe in the PC screen the emitted signal by the remote control and to decode some of its control functions. The construction of the apparatus is easy, very economic, and opening teaching possibilities for high school students and undergraduates.

EDX analysis, microstructure and magnetic properties of CuS doped Bi-2212 superconductors

In this work we have studied the effect of CuS doping on Bi-2212 (nominal composition Bi 2+y Sr 3-y- n Ca n [(CuO) 1-x (CuS) x ] 2 O 6+δ , (0 < x < 0.1, 0 < y < 0.1 and 0.8 < n < 1) superconductors. An improvement in T c of the CuS doped Bi-2212 superconductors is observed in these studies. Most likely improvement in T c of the CuS doped Bi-2212 superconductors is caused by the modifications in the oxygen stoichiometry of the samples due to incorporation of S in the Bi-2212 lattice, with a consequent improvement in hole concentration.

Realizando experimentos didáticos com o sistema de som de um PC

Apresentamos um sistema experimental simples e util para ensino e aprendizagem em cursos de Fisica experimental. Desenvolvemos um sistema experimental com a ajuda de um computador pessoal que funciona ao mesmo tempo como um gerador de funcao e um conversor A/D, o qual pode ser usado como um osciloscopio digital de dois canais e um analisador de espectro, permitindo em tempo real a automacao na aquisicao de dados. Estudamos a resposta em frequencia de um circuito oscilador RLC a uma excitacao do tipo onda quadrada, onde a saida de audio do PC foi usada para produzir uma forma de onda quadrada com frequencia sintonizavel, e sua placa de som para detectar os sinais AC de resposta do circuito. Usamos o circuito RLC como um susceptimetro AC para medir susceptibilidades magneticas de amostras ferromagneticas. Os dados experimentais estao em acordo com a previsao teorica da analise de Fourier. Estudamos ainda um sistema nao linear constituido por um circuito caotico RLD.

Synthesis and study of the structural characteristics of a new complex perovskite oxide Sr2HoHfO5.5 for its use as a substrate for YBCO superconducting films

Abstract A new complex cubic perovskite oxide Sr 2 HoHfO 5.5 has been prepared by solid state reaction process. X-ray diffraction studies show that Sr 2 HoHfO 5.5 has a A 2 BB ′ O 6 type complex cubic perovskite structure and presence of the significant intensities of superstructure reflections in the X-ray spectrum reveal that it is an ordered complex cubic perovskite oxide. The experimental value of the lattice parameter of Sr 2 HoHfO 5.5 , is a =8.1725 A. Based on the doubling of primitive ABO 3 cubic perovskite unit cell, (1/2) a =4.0862 A of Sr 2 HoHfO 5.5 is comparable to the lattice parameter a =3.8227 A of YBCO superconductor. Sr 2 HoHfO 5.5 has good lattice matching (lattice mismatch ∼6%) with YBCO superconductor. The dc magnetic susceptibility of Sr 2 HoHfO 5.5 , measured in the temperature range 5–300 K shows a Curie–Weiss behavior. Using a Curie–Weiss law fitting we obtain a effective magnetic moment per Ho 3+ ion in Sr 2 HoHfO 5.5 of 9.76 μ B . This value is slightly lower than the spin-only moment (10.60 μ B ) expected for an isolated Ho 3+ ion.

Structural and magnetic properties of NiS doped Bi-2212 superconductors

Abstract In this work we have studied the effect of NiS doping on the superconducting properties of the Bi-2212 (nominal composition Bi 2.1 Sr 2.1 Ca 0.8 [(CuO) 1− x (NiS) x ] 2 O 8+ δ ), superconductors. Our studies show that NiS doping stabilizes superconductivity in the system but all the NiS doped samples gave a T c lower than the superconducting transition temperature of pure Bi-2212 superconductors. It appears that NiS substitution for CuO planes and modification of the oxygen content due to S substitution on O places jointly produce strong localization of charge carriers and at the same time increase the hole concentration of the system. These combined phenomena occurring in the Bi 2.1 Sr 2.1 Ca 0.8 [(CuO) 1− x (NiS) x ] 2 O 8+ δ system are responsible for the deterioration of superconductivity of NiS doped Bi-2212 superconductors.

Study of transport properties of CaLaBa[Cu1-xZnx]3O7-δ superconductors

Abstract In this work, the effect of substitution of Zn for Cu on the superconducting properties of CaLaBaCu3O7−δ has been studied. CaLaBa[Cu1−xZnx]3O7−δ samples present a sharp superconducting transition with a transition width that increases with x. The depletion of Tc with x is consistent with a non magnetic disordering model.

Structural and superconducting properties of the composite LaBaCaCu3O7−δ–Ba2HoHfO5.5

Abstract We have successfully fabricated HTS – ceramic insulator composite system LaBaCaCu 3 O 7− δ –Ba 2 HoHfO 5.5 in which particles of the superconductor and insulator materials could coexist with well defined separated phases left intact by stringent high-temperature processing conditions. Addition of Ba 2 HoHfO 5.5 did not have any deteriorating effect on the superconducting properties of the LaBaCaCu 3 O 7− δ superconductor.

EDX analysis and microstructural properties of the Yba2Cu3O7−δ-Ba2HoSbO6 superconducting composites

We have fabricated and characterized Yba2Cu3O7−δ-Ba2HoSbO6a realized high Tcsuperconductor - ceramic insulator composite system in which particles of the superconductor and ceramic insulator could coexist with well defined separated phases left intact by stringent processing conditions. All the composites exhibit superconductivity at 92K. EDX analysis show that element% and atomic% of the composites are in a good agreement with those of their respective components. SEM studies show homogenous surface morphology and particle size distribution. There is no detectable interface interaction between component grains and Ba2HoSbO6grains are distinguishably distributed in the Yba2Cu3O7−δmatrix.