A new system for the control of a piezoelectric device is introduced. It works as a phase shifter in an interference optical microscope. This circuit translates controllable constant frequency signals, generated with a standard sound card, to electrical signals with constant voltage through a frequency-to-voltage converter; this full analog conversion allows for producing voltage steps of 16 lv, which is a better resolution than a commercial digital to analog converter working (in the desired voltage range), and hence, results in an arbitrary phase uncertainty under 3%. The calibration method allows for verification of the displacement's steadfastness in the arbitrary phase, and for diagnosing of errors that could alter the experimental interferograms. To check the system calibration, it was experimentally and successfully tested on a silicon surface with rectangular holes of known depth.

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Se presenta un dispositivo para la determinación del coeficiente de fricción estática diseñado para mejorar la experiencia en la toma de datos, sin sacrificar su contenido didáctico. El sistema, basado en la medición del ángulo crítico de deslizamiento para un objeto sobre un plano inclinado, utiliza un sensor de posición, eliminando el factor tiempo de reacción en la medida. Un microcontrolador ARDUINO UNO, permite la adquisición y registro de datos de posición y ángulo de inclinación del plano en forma simultánea, con lo que se determina el ángulo crítico. Adicionalmente se incluye un mecanismo de variación continua del ángulo del plano mediante una conexión mecánica no solidaria, reduciendo así los movimientos bruscos o la transmisión de vibraciones del motor a la superficie de medición. Con el sistema propuesto se obtienen coeficientes de fricción con un alto grado de reproducibilidad, proporcionando valores que no sobrepasan el 3% de error en las medidas. El sistema fue probado, usando igual metodología, con superficies de diferentes características, obteniéndose resultados satisfactorios. Como prueba de confiabilidad, se utilizó el equipo en un conjunto de experimentos para determinar la influencia de vibraciones mecánicas sobre los resultados.

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III-V family compounds doped with transition metals are promising materials for spintronic applications. Synthesis of an In0.9Mn0.1Sb ingot was thus carried out by direct fusion of the stoichiometric mixture of the constituent elements, followed by controlled cooling. The ingot obtained showed p-type conductivity. Scanning Electron Microscopy (SEM) images show MnSb clusters in an InSb matrix doped with Mn, a result like that found when the compound is obtained using other techniques. Energy-dispersive X-ray spectroscopy (EDS) shows that the atomic ratio of the clusters is Mn/Sb = 0.896 ± 0.025, while the atomic ratio of the matrix is In/Sb = 1.013 ± 0.005. The indexation of the powder X-ray diffraction pattern at room temperature yielded a majority cubic phase of InSb doped with Mn, with a lattice parameter a = 6.474173 Å and cell unit volume V = 271.36Å3 , while non-indexed reflections are associated with the presence of MnSb rich in Sb. The phase transition temperatures were obtained from differential thermal analysis (DTA) measurements on powder samples in evacuated quartz capsules. It can be observed that fusion of the InSb matrix doped with Mn occurs between 485 °C and 528 °C, unlike the congruent fusion of the InSb at 527.7 °C; while the fusion of the Sb-rich MnSb clusters occurs between 494 °C and 509 °C. These temperatures are lower than those reported for the Sb-rich side of the phase diagram of the Mn-Sb binary system, which shows a decrease in the thermal stability of the compounds. The estimated fusion enthalpies for InSb:Mn and antimony-rich MnSb are, respectively, 4.8 Kcal/mol and 117.4 Kcal/mol.