132331 20240301161208.0 doi 10.1088/0957-4484/24/50/505702 sideral 83604 ART-2013-83604 eng Castrillon, Mariana Synthesis and magnetic behaviour of ultra-small bimetallic FeCo/graphite nanoparticles 2013 FeCo-alloy graphite-coated nanoparticles with mean particle diameter under 8 nm have been synthesized following a CVD carbon-deficient method. The superior magnetic properties of FeCo-alloy nanoparticles makes them good candidates to be used as magnetic filler in magneto-polymer composites. Thanks to the protective effect of the graphite shell, FeCo nanoparticles are stable under oxygen atmosphere up to 200 ° C. The as-prepared nanoparticles presented a highly long range chemically ordered core being ferromagnetic at room temperature with a saturation magnetization at room temperature close to the bulk value. After annealing at 750 K the saturation magnetization and the coercive field increase. To investigate the processes involved in the thermal treatment, the temperature dependence of the magnetization and the particle composition, size and structure have been characterized before and after annealing. Besides powder x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS), a detailed study by means of advanced transmission electron microscopy (TEM) techniques has been carried out. In particular, aberration corrected scanning transmission electron microscopy (STEM), has shown that nanoparticles became faceted after the thermal treatment, as a mechanism to reach the thermodynamic equilibrium within the metastable phase. This outstanding feature, not previously reported, leads to an increase of the shape anisotropy, which in turn might be the origin of the observed increase of the coercive field after annealing. Access copy available to the general public Unrestricted info:eu-repo/grantAgreement/ES/DGA/E98-MOLCHIP info:eu-repo/grantAgreement/ES/MINECO/MAT2012-38318-C03-03 info:eu-repo/semantics/openAccess All rights reserved http://www.europeana.eu/rights/rr-f/ 3.672 2013 MATERIALS SCIENCE, MULTIDISCIPLINARY 39 / 246 = 0.159 2013 Q1 T1 PHYSICS, APPLIED 19 / 135 = 0.141 2013 Q1 T1 NANOSCIENCE & NANOTECHNOLOGY 24 / 73 = 0.329 2013 Q2 T1 info:eu-repo/semantics/article info:eu-repo/semantics/acceptedVersion Mayoral, Alvaro (orcid)0000-0002-5229-2717 Urtizberea, Ainhoa (orcid)0000-0002-8424-9780 Marquina, Clara Universidad de Zaragoza (orcid)0000-0003-0602-492X Irusta, Silvia Universidad de Zaragoza (orcid)0000-0002-2966-9088 Meier, Johan Santamaria, Jesus Universidad de Zaragoza (orcid)0000-0002-8701-9745 5005 555 Universidad de Zaragoza Dpto. Ing.Quím.Tecnol.Med.Amb. Área Ingeniería Química 2003 395 Universidad de Zaragoza Dpto. Física Materia Condensa. Área Física Materia Condensada 24, 50 (2013), 505702 [11 pp] Nanotechnology Nanotechnology 0957-4484 1716102 http://zaguan.unizar.es/record/132331/files/texto_completo.pdf Postprint 2391155 http://zaguan.unizar.es/record/132331/files/texto_completo.jpg?subformat=icon icon Postprint oai:zaguan.unizar.es:132331 articulos driver 2024-03-01-14:55:07 ARTICLE