Detection of magnetic moment in thin films with a home-made vibrating sample magnetometer

This paper explores the optimization of an array of pick-up coils in a home-made vibrating sample magnetometer for the detection of magnetic moment in thin films. Sensitivity function of a 4-coils Mallinson configuration was numerically studied for the determination of the physical dimensions that enhance the sensitivity of the magnetometer. By performing numerical simulations using the Biot-Savart law combined with the principle of reciprocity we were able to determine the maximum values of sensitivity and the influence of the separation of the coils on the sensitivity function. After the optimization of the pick-up coils, the vibrating sample magnetometer was able to detect the magnetic moment of a 100 nm-thickness Fe19Ni81 magnetic thin film along and perpendicular to the in-plane anisotropy easy axis. The implemented vibrating sample magnetometer is able to detect changes in the magnetic moment of ∼2 × 10-4 emu.Fil: Jordán, D.. Universidad Nacional de Ingeniería. Facultad de Ciencias; PerúFil: González Chávez, D.. Centro Brasileiro de Pesquisas Físicas; BrasilFil: Laura, D.. Universidad Nacional de Ingeniería. Facultad de Ciencias; PerúFil: Leon Hilario, Ludwin Misael. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Ingeniería. Facultad de Ciencias; PerúFil: Monteblanco, E.. Universite de Lorraine; FranciaFil: Gutarra Espinoza, Abel. Universidad Nacional de Ingeniería. Facultad de Ciencias; PerúFil: Aviles Felix, Luis Steven. Comision Nacional de Energía Atómica. Gerencia de Área Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Bariloche). División Resonancias Magnéticas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Identification of rare-earth minerals associated to K-feldspar: Capacsaya project in Peru

A recently discovered the rare-earth-rich site in Capacsaya, located at 123 km northwest of Cusco, at the south of Peru, contains significant quantities of light and heavy rare-earth elements such as neodymium, lanthanum, cerium, europium, and yttrium. This work reports the identification of rare-earth elements and their associated minerals using scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction analyses. Five (5) samples extracted from different locations at the Capacsaya site were characterized and identified K-feldspar as the mineral associated with the rare-earth elements in a representative sample with a high concentration of lanthanum and cerium. The results showed rare-earth elements contained within the mineral phase monazite, being cerium the dominant element in the phase (La, Ce, Nd)PO4. Finally, through the electrostatic separation process we demonstrate that it was possible to achieve an efficient separation of the K-feldspar phase in the particle size range 75–150 μ m.Fil: Ochoa, J.. Universidad Nacional de Ingeniería; PerúFil: Monteblanco, E.. Commissariat A L Energie Atomique Et Aux Energies Alternatives.; FranciaFil: Cerpa, L.. Instituto Geológico Minero y Metalúrgico; PerúFil: Gutarra Espinoza, Abel. Universidad Nacional de Ingenieria; PerúFil: Aviles Felix, Luis Steven. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología - Nodo Bariloche | Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología - Nodo Bariloche; Argentin

Identification of rare earth minerals associated to K-feldspar: Capacsaya project in Peru

A recently discovered the rare-earth-rich site in Capacsaya, located at 123 km northwest of Cusco, at the south of Peru, contains signifcant quantities of light and heavy rare-earth elements such as neodymium, lanthanum, cerium, europium, and yttrium. This work reports the identifcation of rare-earth elements and their associated minerals using scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray difraction analyses. Five (5) samples extracted from diferent locations at the Capacsaya site were characterized and identifed K-feldspar as the mineral associated with the rare-earth elements in a representative sample with a high concentration of lanthanum and cerium. The results showed rare-earth elements contained within the mineral phase monazite, being cerium the dominant element in the phase (La, Ce, Nd)PO4. Finally, through the electrostatic separation process we demonstrate that it was possible to achieve an efcient separation of the K-feldspar phase in the particle size range 75–150 μm

Affirmative Action Programs in Social Service Agencies: Status of the Female M.S.W.

Job status and salary inequities between men and women have only recently been documented (Kravetz 1976). The federal government, over the past few decades, through various acts and executive orders, has created legislation to prohibit discrimination based on race, sex, color, religion or national origin in all employment practices. The question is to what extent this legislation has permeated social service agencies and affected their employment patterns, particularly with respect to administrative positions. In 1976, the Women\u27s Issues Committee of the Oregon Chapter of the National Association of Social Workers (NASW), addressed this question by initiating a study of social work employment in Oregon. The first part of the study examined the salaries and positions of NASW members in this state. The second part of the study was designed to study more specifically the employment patterns of women MSWs in Oregon\u27s social service agencies. Under the auspices of the Women\u27s Issues Committee, the second part of the study was designed and conducted by eight graduate students at the School of Social Work at Portland State University. One objective of the study was to find out the proportion of men and women filling the management positions in local social service agencies. But the primary purpose of the study was to examine the management-executive employment patterns in agencies before and after affirmative action programs were instituted. An attempt was then made to determine the effects, if any, of such programs. It was hoped that the results would clarify how agencies implement their affirmative action programs, the effects of implementation, and the barriers to the employment of women in management positions

Procesos de separación magnética y electrostática de tierras raras: caso de estudio Proyecto Capacsaya, norte del Cusco

En este trabajo presentamos los avances realizados en la puesta en funcionamiento y optimización de dos técnicas utilizadas en el proceso de obtención de TRs en 20 muestras del proyecto, las cuales fueron seleccionadas de acuerdo a su alto contenido en TRs. En la primera etapa, para la obtención de los materiales magnéticos, se desarrollaron dos técnicas: (i) la separación magnética (Oberteuffer, 1974) y (ii) la separación electrostática (Wu 2009)

Synthesis and characterization of TiN / Ti / AISI 410 coatings

The synthesis and characterization of Ti and TiN thin films of different thicknesses was carried out on a martensitic stainless steel AISI 410 substrate used for tool manufacturing. The mechanical parameters between the interacting surfaces such as thickness, adhesion and hardness were measured. By means of the scanning electron microscope (SEM) the superficial morphology of the Ti/TiN interface was observed, finding that the growth was of columnar grains and by means of EDAX the existence of titanium was verified.  Using X-ray diffraction (XRD) it was possible to observe the presence of residual stresses (~ -3.1 GPa) due to the different crystalline phases in the coating. Under X-ray photoemission spectroscopy (XPS) it was possible to observe the molecular chemical composition of the coating surface, being Ti-N, Ti-N-O and Ti-O the predominant ones

Spin transfer torque nano-oscillators based on synthetic ferrimagnets: Influence of the exchange bias field and interlayer exchange coupling

International audienceA comprehensive numerical study of the spin toque driven dynamic states is presented for a synthetic ferrimagnet. For this, the Landau-Lifshitz-Gilbert equation has been solved simultaneously for the two coupled layers of the synthetic ferrimagnet in a macrospin approach including the spin transfer torque term from an external polarizer for one of them. It is shown that a large variety of dynamic modes (in-plane precession (IPP) and out-of-plane precession) can be established, upon varying the strength of the exchange bias field that pins one of the layers of the SyF as well as the Ruderman-Kittel-Kasuya-Yosida interlayer coupling strength. The current—field state diagrams are presented as well as the frequency current dependencies of the most important mode which is the IPP mode. A characteristic feature of the IPP mode for the coupled system (as compared to single layer excitations) is the change, increase or decrease of the frequency, with current upon increasing field. It is shown that this strongly depends on the asymmetry of the internal fields that the two layers experience, upon varying either their thickness or the exchange bias field

Transmission of high-energy electrons through metal-semiconductor Schottky junctions

International audienceUsing the electron beam of a scanning electron microscope as an external current source with tunable energy, we investigate the transport properties of high-energy electrons injected from vacuum into the metal layer of Pt/Cu/Si Schottky junctions. When the injection energy is varied between 1 and 30 keV, the current transmitted into the semiconductor increases by several orders of magnitude and reaches values orders of magnitude larger than the current injected from vacuum. Inspecting the energy dependence of the transmitted current we identify two transport regimes. In the limit of low injection energies and thick metal films, the transport is dominated by the formation and propagation of a secondary electron distribution in the metal layer. However, when the injection energy is sufficiently large and the metal layer sufficiently thin, electrons are transmitted into the semiconductor with negligible energy loss, i.e., the metal layer becomes essentially transparent. The transmitted current is then dominated by impact ionization in the semiconductor. When the metal layer of the Schottky junction is relatively thick and the injection energy of a few keV typically, the transmitted current increases abruptly. The origin of this abrupt change is interpreted as a combined effect of a quasiballistic electron transport in the metal layer and a sudden variation of the density of states in the semiconductor substrate