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Se construyó un magnetómetro de efecto Kerr superficial (MEKS) para medir las propiedades magnéticas de películas delgadas de Permalloy (Ni81Fe19) de 20 nm de espesor. Se encontró que el campo coercitivo de las muestras tiene valores entre 2-6 Oe. Las películas mostraron anisotropía uniaxial en el plano y se identificaron los ejes de fácil y difícil magnetización. Se midió el ángulo de Kerr para las configuraciones longitudinal y polar y la saturación magnética para diferentes ángulos de incidencia de haz de luz. Los resultados fueron comparados satisfactoriamente con los obtenidos con un Magnetómetro de Muestra Vibrante (MMV).

A surface Kerr effect magnetometer (MEKS) was built to measure the magnetic properties of Permalloy (Ni81Fe19) thin films of 20 nm thickness. It was found that the coercive field of the samples has values between 2-6 Oe. The films showed in-plane uniaxial anisotropy and axes of easy and difficult magnetization were identified. The Kerr angle was measured for the longitudinal and polar configurations and the magnetic saturation for different angles of incidence of the light beam. The results were satisfactorily compared with those obtained with a Vibrating Sample Magnetometer (VSM).

In this work, we describe the design and construction of a system to measure the angular light scattering distribution from small dielectric spheres suspended in water, using a laser as the light source. It also covers the development of an optical detection system to improve the signal‐to‐noise ratio. We report on the experimental measurements of light scattering from colloidal suspensions of latex spheres with nominal diameters of 0.49 and 1.03 µm and a coefficient of variation of 3%. Two lasers with different wavelengths (632.8 and 532.0 nm) were used to observe the variation of the angular scattering distribution. The experimental results were then compared with angular scattering distributions generated from Mie theory, in order to determine the particle size. We obtained diameters of 0.49 and 0.95 µm, with a relative accuracy of 6.1 and 5.3%, respectively.  

 The Atomic Force Microscope (AFM) using a tuning fork as probe requires very sharp and light tips for obtaining topographic images with great resolution. On the other hand, Scanning Tunneling Microscopes (STM) needs sharp and conducting tips. Both requirements can be achieved using carbon fiber as the base material for the fabrication of the tips, with the additional advantage of being a material with a very low tendency to oxidize. In this work some initial results of the anodic dissolution technique are presented, which has permitted us to obtain the apex size of the tips in the nanometer scale. The electrochemical cell consists of the carbon fiber as the anode (7m diameter), a 2mm diameter Platinum ring as the cathode and Potassium Hydroxide as the electrolyte. A drop of the electrolyte is deposited on the Platinum ring and after that the carbon fiber is introduced into the d...

En este trabajo se describe el diseño y la construcción de un sistema para medir la distribución angular del scattering de luz de micro esferas dieléctricas suspendidas en agua, usando un láser como fuente de luz. El trabajo cubre el desarrollo de un sistema de detección óptico para mejorar la relación señal ruido. Reportamos medidas experimentales de scattering de luz de suspensiones coloidales de esferas de látex con diámetros nominales de 0,49 y 1,03 µm, y un coeficiente de variación de 3%. Se utilizaron dos láseres de diferentes longitudes de onda, 632,8 y 532,0 nm, para observar la variación de la distribución angular de scattering. Los resultados experimentales fueron comparados con distribuciones de scattering angular generadas por la teoría de Mie para determinar el tamaño de partícula. Los diámetros obtenidos fueron 0,49 y 0,95 µm con una incertidumbre relat...

Los microscopios de Fuerza Atómica (AFM) con sonda diapasón requieren puntas muy agudas y livianas para obtener imágenes topográficas de gran resolución. Por otro lado, los microscopios de Efecto Túnel (STM) necesitan puntas agudas y conductoras. Ambos requerimientos pueden ser obtenidos usando fibras de carbono como material base para la fabricación de las puntas, con la ventaja adicional de ser un material con bajo nivel de oxidación. En este trabajo se presentan algunos resultados iniciales de la técnica de disolución anódica que ha permitido obtener puntas de carbono de rango nanométrico. La celda electroquímica consistió en la fibra de carbono como ánodo (7m de diámetro), un anillo de platino de 2mm de diámetro como cátodo y KOH como electrolito. Una gota del electrolito se suspendió del anillo de platino para posteriormente introducir la fibra dentro de la got...

 The Atomic Force Microscope (AFM) using a tuning fork as probe requires very sharp and light tips for obtaining topographic images with great resolution. On the other hand, Scanning Tunneling Microscopes (STM) needs sharp and conducting tips. Both requirements can be achieved using carbon fiber as the base material for the fabrication of the tips, with the additional advantage of being a material with a very low tendency to oxidize. In this work some initial results of the anodic dissolution technique are presented, which has permitted us to obtain the apex size of the tips in the nanometer scale. The electrochemical cell consists of the carbon fiber as the anode (7m diameter), a 2mm diameter Platinum ring as the cathode and Potassium Hydroxide as the electrolyte. A drop of the electrolyte is deposited on the Platinum ring and after that the carbon fiber is introduced into the d...

In this work, we describe the design and construction of a system to measure the angular light scattering distribution from small dielectric spheres suspended in water, using a laser as the light source. It also covers the development of an optical detection system to improve the signal‐to‐noise ratio. We report on the experimental measurements of light scattering from colloidal suspensions of latex spheres with nominal diameters of 0.49 and 1.03 µm and a coefficient of variation of 3%. Two lasers with different wavelengths (632.8 and 532.0 nm) were used to observe the variation of the angular scattering distribution. The experimental results were then compared with angular scattering distributions generated from Mie theory, in order to determine the particle size. We obtained diameters of 0.49 and 0.95 µm, with a relative accuracy of 6.1 and 5.3%, respectively.  

In this paper, the construction of a wireless data acquisition system is described. The system enable us monitoring process that are developed in hazardous environments, or other physical phenomena that must be realized far away the laboratory. Three basic units compose the system: analogic to digital converter with transmitter, receiver, and the PC with application software.

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En este artículo se describe la construcción de un sistema inalámbrico. El sistema permite el monitoreo de procesos que se desarrollan en ambientes corrosivos u otros fenómenos físicos que se realizan lejos del laboratorio. El sistema se compone de tres partes principales: el conversor analógico a digital con su transmisor, el receptor y la computadora con software de aplicación.

Se prepararon óxidos mixtos de la serie La1-x SrxMnO3 ± 8 (x=0.0-0.5) por el método de citratos. La caracterización se realizó estructuralmente por difracción de rayos X (XRD) y elementalmente por acoplamiento inductivo de plasma (ICP). La relación Mn4+/Mn3+ del óxido se determinó por yodometría. El área específica de la muestra en polvo se determinó por BET Las propiedades de transporte electrónico para diferentes niveles de sustitución de La se hicie­ron a diferentes temperaturas entre 300-700 K. Los resultados de la caracterización nos demuestran que nuestra técnica de fabricación produce óxidos del tipo La1-x SrxMnO3 ± 8 con propiedades favorables para ser utilizados como cátodos en celdas de combustible.

In this paper, the construction of a wireless data acquisition system is described. The system enable us monitoring process that are developed in hazardous environments, or other physical phenomena that must be realized far away the laboratory. Three basic units compose the system: analogic to digital converter with transmitter, receiver, and the PC with application software.

Mixed oxides of the La, Sr MnO, ± (x=0.0-0.5) series were prepared by the citrate method. The characterization was carried out structurally by X-ray diffraction (XRD) and elementally by inductive plasma coupling.(ICP). The Mn/Mn" ratio of the oxide was determined by iodometry. The specific area of ​​the powder sample wasdetermined by BET. The electronic transport properties for different levels of La substitution were done at different temperatures between 300-700 K. The characterization results show us that our manufacturing technique produces oxides of the La, Sr MnOs type with favorable properties to be used as cathodes in fuel cells.

This paper describes the implementation and a detailed optimization of a Vibrating Sample Magnetometer (VSM) for an undergraduate physics course laboratory. The VSM operation parameters were extensively discussed using Foner and Mallison coils configuration. The influence of the involved parameters (e.g. oscillation frequency, oscillation amplitude, rate change of the external magnetic field, coils configuration, etc.) on the induced voltage in the pick-up coils were discussed. A disk of nickel of 6-mm diameter was used for the calibration of the magnetometer, comparing the hysteresis loop measured with our magnetometer with the one obtained using a commercial VSM. Magnetization curves of two different samples were obtained in order to test the sensitivity of the magnetometer. The vibrating sample magnetometer implemented in the present work is able to detect changes in the total magneti...

Este artículo describe la implementación y una optimización detallada de un magnetómetro de muestra vibrante (VSM) para un laboratorio de licenciatura en física. Los parámetros de operación de VSM se discutieron ampliamente usando la configuración de bobinas de Foner y Mallison. Se discutió la influencia de los parámetros implicados (por ejemplo, frecuencia de oscilación, amplitud de oscilación, cambio de velocidad del campo magnético externo, configuración de bobinas, etc.) sobre la tensión inducida en las bobinas de captación. Se utilizó un disco de níquel de 6 mm de diámetro para la calibración del magnetómetro, comparando el bucle de histéresis medido con nuestro magnetómetro con el obtenido utilizando un VSM comercial. Se obtuvieron curvas de magnetización de dos muestras diferentes para probar la sensibilidad del magnetómetro. El magnetómetro de muestra vi...

This paper describes the implementation and a detailed optimization of a Vibrating Sample Magnetometer (VSM) for an undergraduate physics course laboratory. The VSM operation parameters were extensively discussed using Foner and Mallison coils configuration. The influence of the involved parameters (e.g. oscillation frequency, oscillation amplitude, rate change of the external magnetic field, coils configuration, etc.) on the induced voltage in the pick-up coils were discussed. A disk of nickel of 6-mm diameter was used for the calibration of the magnetometer, comparing the hysteresis loop measured with our magnetometer with the one obtained using a commercial VSM. Magnetization curves of two different samples were obtained in order to test the sensitivity of the magnetometer. The vibrating sample magnetometer implemented in the present work is able to detect changes in the total magneti...

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