Magnetic glass in Shape Memory Alloy : Ni45Co5Mn38Sn12

The first order martensitic transition in the ferromagnetic shape memory alloy Ni45Co5Mn38Sn12 is also a magnetic transition and has a large field induced effect. While cooling in the presence of field this first order magnetic martensite transition is kinetically arrested. Depending on the cooling field, a fraction of the arrested ferromagnetic austenite phase persists down to the lowest temperature as a magnetic glassy state, similar to the one observed in various intermetallic alloys and in half doped manganites. A detailed investigation of this first order ferromagnetic austenite (FM-A) to low magnetization martensite (LM-M) state transition as a function of temperature and field has been carried out by magnetization measurements. Extensive cooling and heating in unequal field (CHUF) measurements and a novel field cooled protocol for isothermal MH measurements (FC-MH) are utilized to investigate the glass like arrested states and show a reverse martensite transition. Finally, we determine a field -temperature (HT) phase diagram of Ni45Co5Mn38Sn12 from various magnetization measurements which brings out the regions where thermodynamic and metastable states co-exist in the HT space clearly depicting this system as a 'Magnetic Glass'.Comment: Magnetic field tunes kinetic arrest and CHUF shows devitrification and melting of Magnetic glas

La formación profesional vista desde los estudiantes en situación de discapacidad auditiva

Esta investigación tiene como objetivo central Comprender las experiencias de formación profesional de dos (02) jóvenes en situación de discapacidad auditiva en la Corporación Universitaria Minuto de Dios Sede principal en el segundo semestre de 2014, como técnicas se utilizó la observación participante, las entrevistas semi-estructuradas, a partir del análisis de estas se plantearon las categorías de análisis: Educación Inclusiva, Experiencias, Trabajo Social y discapacidad, los resultados que se obtuvieron están de acuerdo a cada categoría y responden a cada experiencia vivida delas estudiantes en situación de discapacidad en la formación profesiona

Nanometric Particle Size And Phase Controlled Synthesis And Characterization Of γ-fe2o3 Or (α + γ)-fe2o3 By A Modified Sol-gel Method

Fe2O3 nanoparticles with sizes ranging from 15 to 53 nm were synthesized by a modified sol-gel method. Maghemite particles as well as particles with admixture of maghemite and hematite were obtained and characterized by XRD, FTIR, UV-Vis photoacoustic and Mössbauer spectroscopy, TEM, and magnetic measurements. The size and hematite/maghemite ratio of the nanoparticles were controlled by changing the Fe:PVA (poly (vinyl alcohol)) monomeric unit ratio used in the medium reaction (1:6, 1:12, 1:18, and 1:24). The average size of the nanoparticles decreases, and the maghemite content increases with increasing PVA amount until 1:18 ratio. The maghemite and hematite nanoparticles showed cubic and hexagonal morphology, respectively. Direct band gap energy were 1.77 and 1.91 eV for A6 and A18 samples. Zero-field-cooling-field-cooling curves show that samples present superparamagnetic behavior. Maghemite-hematite phase transition and hematite Néel transition were observed near 700 K and 1015 K, respectively. Magnetization of the particles increases consistently with the increase in the amount of PVA used in the synthesis. Mössbauer spectra were adjusted with a hematite sextet and maghemite distribution for A6, A12, and A24 and with maghemite distribution for A18, in agreement with XRD results. © 2013 AIP Publishing LLC.11410Xu, P., Zeng, G.M., Huang, D.L., Feng, C.L., Hu, S., Zhao, M.H., Lai, C., Liu, Z.F., (2012) Sci. Total Environ., 424, pp. 1-10. , 10.1016/j.scitotenv.2012.02.023Rajabi, F., Karimi, N., Saidi, M.R., Primo, A., Varma, R.S., Luque, R., (2012) Adv. Synth. Catal., 354, pp. 1707-1711. , 10.1002/adsc.201100630Kitamuraa, H., Zhaob, L., Hangc, B.T., Okadab, S., Yamaki, J.-I., (2012) J. Power Sources, 208, pp. 391-396. , 10.1016/j.jpowsour.2012.02.051Figuerola, A., Di Corato, R., Manna, L., Pellegrino, T., (2010) Pharmacol. 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Magnetocaloric Effect In Fecr Soft Magnetic Nanocrystalline Alloys

In this work the magnetocaloric effect in a Fe63.5Cr10Si13.5B9CuNb3 soft magnetic nanocrystalline alloy is analysed. High resolution transmission electron microscocopy indicates the precipitation of the desired nanocrystalline structure (grains around 10 nm in size surrounded by a residual amorphous phase) upon suitable treatments of the initial amorphous sample. The temperature dependence of the magnetic entropy variation, Δ SM (T), calculated from the magnetization curves displays a maximum negative value around the Curie temperature of the residual amorphous phase (TC, a ≈ 180 K). The dependence of Δ SM (T) on the applied field and its evolution with the nanocrystalline volume fraction indicates the main contribution of the residual amorphous phase to the magnetic entropy change. Some specific low temperature magnetization features (spin freezing) are also analysed in terms of Δ SM (T). © 2007 Elsevier B.V. All rights reserved.3162 SPEC. ISS.e876e878Giauque, W.F., Macdougall, D.P., (1933) Phys. Rev., 43, p. 768Zimm, C., Stenberg, A., Pecharsky, V., Gschneider Jr., K., Osborne, M., Anderson, I., (1998) Adv. Cryog. Eng., 43, p. 1759Tishin, A.M., Spichkin, Y.I., (2003) The Magnetocaloric effect and its application, , IOP Publishing Ltd, London, UKTegus, O., Brück, E., Zhang, L., Dagula, Buschow, K.H.J., de Boer, F.R., (2002) Physica B, 319, p. 174Shir, F., Yanik, L., Bennet, L.H., DellaTorre, E., Shull, R.D., (2003) J. Appl. Phys., 93, p. 8295Didukh, P., Slawska-Waniewska, A., (2003) J. Magn. Magn. Mater., 254-255, p. 407Franco, V., Blázquez, J.S., Conde, C.F., Conde, A., (2006) Appl. Phys. Lett., 88, p. 042505Skorvánek, I., Kovác, KJ., Czecholovak, (2005) J. Phys., 54, pp. D189Gomez-Polo, C., Li, Y., Pérez-Landazabal, J.I., Recarte, V., Vázquez, M., (2003) Sensors and Actuators A, 1-3, p. 230Gómez-Polo, C., Pérez-Landazabal, J.I., Recarte, V., (2003) IEEE Trans. Magn., 39, p. 3019Hernando, A., Kulik, T., (1994) Phys. Rev. B, 49, p. 7064Skorvánek, I., Skwirblies, S., Kötzler, J., (2001) Phys. Rev. B, 64, p. 184437Shen, T.D., Schwarz, R.B., Coulter, J.Y., Thomson, J.D., (2002) J. Appl. Phys., 91, p. 524

Effect of Annealing Temperature on Magnetic After-Effect in FeCuNbSiB Alloys

The microstructure and magnetic properties i.e. the initial permeability, magnetic after-effect and coercivity for the as-quenched and annealed at different temperatures Fe73.5Cu1Nb3Si13.5B9 samples are studied. After annealing the samples at 573 K for 1 h the decrease of the initial permeability and increase of the disaccommodation amplitude are observed. These are connected with a local anisotropy induced during this treatment. The increase of the annealing temperature causes the improvement of soft magnetic properties. However, after annealing the toroidal samples at 723 K for 1 h a magnetic hardening is observed. It seems to be connected with the appearance of αFe-Si nuclei and clusters enriched in Cu. Moreover, it was stated that the cooling conditions of the samples influence also their magnetic properties. Therefore, the values of coercivity obtained for annealed strips in comparison with corresponding results of µ' obtained for toroids are shifted towards higher temperature by 50 K

Mechanical Spectroscopy in Fe-Al-Si alloys at Elevated Temperatures

The mechanical spectroscopy response in Fe-25 at.% (Al + Si) and Fe-15 at.% (Al + Si) has been studied in the temperature interval between800 and 1200 K. The solute grain boundary relaxation of aluminium and silicon was strongly dependent of the degree of order in the sample. Adecrease in the order degree allows the development of the solute peak at around 1000K during the cooling from 1200 K. Nevertheless, if the orderdegree is not decreased, the grain boundaries remain locked and consequently the relaxation peak does not appear

Nanometric particle size and phase controlled synthesis and characterization of gamma-Fe2O3 or (alpha plus gamma)-Fe2O3 by a modified sol-gel method

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fe2O3 nanoparticles with sizes ranging from 15 to 53 nm were synthesized by a modified sol-gel method. Maghemite particles as well as particles with admixture of maghemite and hematite were obtained and characterized by XRD, FTIR, UV-Vis photoacoustic and Mossbauer spectroscopy, TEM, and magnetic measurements. The size and hematite/maghemite ratio of the nanoparticles were controlled by changing the Fe:PVA (poly (vinyl alcohol)) monomeric unit ratio used in the medium reaction (1:6, 1:12, 1:18, and 1:24). The average size of the nanoparticles decreases, and the maghemite content increases with increasing PVA amount until 1:18 ratio. The maghemite and hematite nanoparticles showed cubic and hexagonal morphology, respectively. Direct band gap energy were 1.77 and 1.91 eV for A6 and A18 samples. Zero-field-cooling-field-cooling curves show that samples present superparamagnetic behavior. Maghemite-hematite phase transition and hematite Neel transition were observed near 700K and 1015 K, respectively. Magnetization of the particles increases consistently with the increase in the amount of PVA used in the synthesis. Mossbauer spectra were adjusted with a hematite sextet and maghemite distribution for A6, A12, and A24 and with maghemite distribution for A18, in agreement with XRD results. (C) 2013 AIP Publishing LLC.11410Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)MCI [Spain-PHB 2008-0044-PC]Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)CAPES [184-09]MCI [Spain-PHB 2008-0044-PC