2026-06-29T07:49:41Zhttps://docta.ucm.es/rest/oai/request

oai:docta.ucm.es:20.500.14352/1366662026-05-13T00:01:18Zcom_20.500.14352_14col_20.500.14352_15

Sol-gel synthesis control of iron-cobalt alloy/ferrite core/shell nanoparticles supported by a carbon medium with semi-hard magnetic features Castellano Soria, Alberto López Sánchez, Jesús Serrano, Aida Gorni, Giulio Varela Del Arco, María Sardinero, Ignacio Carmona Tejero, Noemí Hernando Grande, Antonio Marín Palacios, María Pilar Navarro Palma, Elena We explore a simple and optimized approach for obtaining magnetic nanoparticle-carbon composites by a novel one-pot sol-gel method. In them, various metal cations ratios of Fe3+ and Co2+ are evaluated. The ratio of Fe:Co is a critical parameter that governs the presence of different crystalline phases with tailored magnetic properties. Interestingly, the smallest introduction of Co into the synthesis (19Fe:1Co) provides an abrupt emergence of the body-centered cubic (bcc) Fe-Co alloy, instead of the orthorhombic Pnma structure characteristic of the Fe3C intermetallic compound (1Fe:0Co). Advanced structural and electronic characterizations reveal the formation of Fe-Co/Co-ferrite core/shell nanoparticle structures embedded in a carbon matrix. The sphere-like nanoparticles range from 10 to 45 nm and the shells show a spinel structure with a thickness of 2–3 nm. In addition, X-ray absorption spectroscopy unveils that the oxidation state of Fe and Co cations is close to zero, demonstrating their predominant metallic character. The magnetic properties can be modulated by a precise control of the alloy composition varying the Co content, displaying saturation magnetization values close to ∼137 emu/g. The nanoparticles are mainly single magnetic domain with a considerable coercive field (∼450 Oe), higher than those reported in the literature for Fe-Co nanoparticles. This semi-hard character is due to a notable spring exchange effect emerged by passivating the surface of Fe-Co-bcc cores with a thin Co-ferrite-like shell 2026-05-12T15:54:17Z 2026-05-12T15:54:17Z 2026-05-12T15:54:17Z 2023-10 journal article https://hdl.handle.net/20.500.14352/136666 0925-8388 10.1016/j.jallcom.2023.170244 1873-4669 eng info:eu-repo/grantAgreement/MINECO//MAT2015-65445-C2-1-R/ES/RECUBRIMIENTOS MULTIFUNCIONALES MODIFICADOS CON AGENTES DE RETROALIMENTACION ACTIVA PARA LA PROTECCION DE ALEACIONES LIGERAS DE INTERES EN AERONAUTICA Y AUTOMOCION/ info:eu-repo/grantAgreement/AEI/Plan Estatal de Investigación Científica y Técnica y de Innovación 2013-2016/MAT2017-86450-C4-1-R/ES/DISEÑO DE PROCESOS DE SINTERIZACION EN FRIO PARA NUEVOS MATERIALES NANOESTRUCTURADOS/ info:eu-repo/grantAgreement/MINECO//MAT2015-67557-C2-1-P/ES/NANOPARTICULAS Y NANOESTRUCTURAS MAGNETICAS FUNCIONALES PARA LA ACTIVACION TERMICA Y CONTROL IN-SITU DE PROCESOS FISICOS Y QUIMICOS/ info:eu-repo/grantAgreement/AEI/Plan Estatal de Investigación Científica y Técnica y de Innovación 2017-2020/RTI2018-095856-B-C21/ES/DESARROLLO DE MATERIALES MAGNETICOS Y SENSORES PARA APLICACIONES BIOMEDICAS/ info:eu-repo/grantAgreement/AEI/Plan Estatal de Investigación Científica y Técnica y de Innovación 2017-2020/RTI2018-095303-A-C52/ES/INTERFACIAL MAGNETISM FOR ULTRAFAST AND LOW DISSIPATION SIGNAL PROCESSING DEVICES/ PIE-2021-60-E-030 PIE-2010-6-OE- 013 info:eu-repo/grantAgreement/AEI/Plan Estatal de Investigación Científica y Técnica y de Innovación 2021-2023/PID2021-122980OB-C55/ES/SIMULACIONES MULTIESCALA PARA EL CONTROL DE ORDENES MAGNETICOS COMPLEJOS EN ESPINORBITRONICA/ 2013/MIT-2850/NANOFRONTMAG 2018/NMT-4321/NANOMAGCOST A. Castellano-Soria, J. López-Sánchez, A. Serrano, G. Gorni, M. Varela, I. Sardinero, N. Carmona, A. Hernando, P. Marín, E. Navarro, Sol-gel synthesis control of iron-cobalt alloy/ferrite core/shell nanoparticles supported by a carbon medium with semi-hard magnetic features, Journal of Alloys and Compounds 959 (2023) 170244. https://doi.org/10.1016/j.jallcom.2023.170244. http://creativecommons.org/licenses/by-nc-nd/4.0/ open access Attribution-NonCommercial-NoDerivatives 4.0 International Elsevier