Surface spin-glass freezing in interacting core-shell NiO nanoparticles (Articolo in rivista)

Type
Label
  • Surface spin-glass freezing in interacting core-shell NiO nanoparticles (Articolo in rivista) (literal)
Anno
  • 2008-01-01T00:00:00+01:00 (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#doi
  • 10.1088/0957-4484/19/18/185702 (literal)
Alternative label
  • Winkler E. (1); Zysler R.D. (1); Vasquez Mansilla M. (2); Fiorani D. (2); Rinaldi D. (3); Vasilakaki M. (4); Trohidou K. N. (4) (2008)
    Surface spin-glass freezing in interacting core-shell NiO nanoparticles
    in Nanotechnology (Bristol. Print)
    (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
  • Winkler E. (1); Zysler R.D. (1); Vasquez Mansilla M. (2); Fiorani D. (2); Rinaldi D. (3); Vasilakaki M. (4); Trohidou K. N. (4) (literal)
Pagina inizio
  • 185702 (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#numeroVolume
  • 19 (literal)
Rivista
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#note
  • http://dx.doi.org/10.1088/0957-4484/19/18/185702 (literal)
Note
  • ISI Web of Science (WOS) (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni
  • (1) Consejo Nacl Invest Cient & Tecn, CNEA, Ctr Atom Bariloche, RA-8400 San Carlos De Bariloche, Rio Negro Argentina; (2) CNR, Ist Struttura Mat, Area Ric Roma, CP 10, I-00016 Monterotondo, Italy; (3) Università Politecnica Marche Brecce Bianche, Dipartimento Fis & Ingn Mat Territorio, I-60131 Ancona, Italy; (4) NCSR Demokritos, Institute Materials Science, GR-15310 Athens, Greece (literal)
Titolo
  • Surface spin-glass freezing in interacting core-shell NiO nanoparticles (literal)
Abstract
  • Magnetization and AC susceptibility measurements have been performed on similar to 3 nm NiO nanoparticles in powder form. The results indicate that the structure of the particles can be considered as consisting of an antiferromagnetically ordered core, with an uncompensated magnetic moment, and a magnetically disordered surface shell. The core magnetic moments block progressively with decreasing temperature, according to the distribution of their anisotropy energy barriers, as shown by a broad maximum of the low field zero-field-cooled magnetization (M-ZFC) and in the in-phase component chi' of the AC susceptibility, centred at similar to 70 K. On the other hand, surface spins thermally fluctuate and freeze in a disordered spin-glass-like state at much lower temperature, as shown by a peak in M-ZFC (at 17 K, for H = 50 Oe) and in chi'. The temperature of the high temperature chi' peak changes with frequency according to the Arrhenius law; instead, for the low temperature maximum a power law dependence of the relaxation time was found, tau = tau(0)(T-g/(T(nu) - T-g))(alpha), where alpha = 8, like in spin glasses, tau(0) = 10(-12) s and T-g = 15.9 K. The low temperature surface spin freezing is accompanied by a strong enhancement of magnetic anisotropy, as shown by the rapid increase of coercivity and high field susceptibility. Monte Carlo simulations for core/shell antiferromagnetic particles, with an antiferromagnetic core and a disordered shell, reproduce the qualitative behaviour of the temperature dependence of the coercivity. Interparticle interactions lead to a shift to a high temperature of the distribution of the core moment blocking temperature and to a reduction of magnetization dynamics. (literal)
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