32454 20210121082902.0 doi 10.1063/1.4935146 sideral 92357 ART-2015-92357 eng Torres, T. E. Validity of the Néel-Arrhenius model for highly anisotropic CoxFe3-xO4 nanoparticles 2015 Access copy available to the general public Unrestricted We report a systematic study on the structural and magnetic properties of CoxFe3_xO4 magnetic nanoparticles with sizes between 5 and 25 nm, prepared by thermal decomposition of Fe(acac)3 and Co(acac)2. The large magneto-crystalline anisotropy of the synthesized particles resulted in high blocking temperatures (42 K < TB < 345 K for 5 < d < 13 nm) and large coercive ¿elds (HC ~ 1600 kA/m for T ¼ 5 K). The smallest particles (hdi¼5 nm) revealed the existence of a mag-netically hard, spin-disordered surface. The thermal dependence of static and dynamic magnetic properties of the whole series of samples could be explained within the Neel–Arrhenius relaxation framework by including the thermal dependence of the magnetocrystalline anisotropy K1(T), without the need of ad-hoc corrections. This approach, using the empirical Br€ukhatov-Kirensky relation, provided K1(0) values very similar to the bulk material from either static or dynamic magnetic measurements, as well as realistic values for the response times (s0 ~ 10^-10s). Deviations from the bulk anisotropy values found for the smallest particles could be qualitativelyconstant explained based on Zener’s relation between K1(T) and M(T). info:eu-repo/grantAgreement/ES/MINECO/MAT2010-19326 info:eu-repo/grantAgreement/ES/MINECO/MAT2013-42551 info:eu-repo/semantics/openAccess All rights reserved http://www.europeana.eu/rights/rr-f/ 2.101 2015 PHYSICS, APPLIED 47 / 145 = 0.324 2015 Q2 T1 0.821 2015 Physics and Astronomy (miscellaneous) 2015 Q2 info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion Lima Jr., E. (orcid)0000-0002-5229-2717 Mayoral, A. Ibarra, A. Marquina, C. Ibarra, M. R. Goya, G. F. 118 (2015), 183902 [11 pp] J. appl. physi. Journal of Applied Physics 0021-8979 2853481 http://zaguan.unizar.es/record/32454/files/texto_completo.pdf Versión publicada 131062 http://zaguan.unizar.es/record/32454/files/texto_completo.jpg?subformat=icon icon Versión publicada oai:zaguan.unizar.es:32454 articulos driver 2021-01-21-08:16:20 ARTICLE