caa a22 4500 463224760 CHVBK 20180405153223.0 cr unu---uuuuu 170326e20070401xx s 000 0 eng 10.1007/s10853-006-0601-y doi (NATIONALLICENCE)springer-10.1007/s10853-006-0601-y Superparamagnetic relaxation evidences large surface contribution for the magnetic anisotropy of MnFe204 nanoparticles of ferrofluids [Elektronische Daten] [C. Alves, Renata Aquino, Jérôme Depeyrot, Francisco Tourinho, Emmanuelle Dubois, Régine Perzynski] Manganese ferrite nanoparticles, in the size range 3.3-9.0 nm, are prepared by a hydrothermal coprecipitation process and peptized in aqueous solution. The magnetization curves recorded at room temperature on diluted colloidal sols allow characterizing the distribution of magnetic moment by using a simple Langevin formalism. Mössbauer spectroscopy measurements performed on powder samples at 77K exhibit a quadrupolar doublet which intensity grows at the expense of the hyperfine sextet pattern as the nanoparticles mean size decreases. The magnetic dynamics behavior is then investigated by measurements of magnetic hysteretic properties at 5 K and temperature dependence of the zero field cooling (ZFC) susceptibility. The values found for the effective anisotropy constant and the dependence of the irreversibility field, inversely proportional to the reference size, clearly indicate that the magnetic anisotropy of our nanoparticles finds its origin on the disordered surface layer. Springer Science+Business Media, LLC, 2007 Alves C. Complex Fluid Group, Instituto de Física, Universidade de Brasília, CP 04455, 70919-970, Brasília, DF, Brazil aut Aquino Renata Complex Fluid Group, Instituto de Física, Universidade de Brasília, CP 04455, 70919-970, Brasília, DF, Brazil aut Depeyrot Jérôme Complex Fluid Group, Instituto de Física, Universidade de Brasília, CP 04455, 70919-970, Brasília, DF, Brazil aut Tourinho Francisco Complex Fluid Group, Instituto de Química, Universidade de Brasília, CP 04478, 70919-970, Brasília, DF, Brazil aut Dubois Emmanuelle Laboratoire des Liquides Ioniques et Interfaces Chargées, Université Pierre et Marie Curie, Bât. F, Case 63, 4 place Jussieu, 75252, Paris Cedex 05, France aut Perzynski Régine Laboratoire des Liquides Ioniques et Interfaces Chargées, Université Pierre et Marie Curie, Bât. F, Case 63, 4 place Jussieu, 75252, Paris Cedex 05, France aut Journal of Materials Science Kluwer Academic Publishers-Plenum Publishers; http://www.springer-ny.com 42/7(2007-04-01), 2297-2303 0022-2461 42:7<2297 2007 42 10853 https://doi.org/10.1007/s10853-006-0601-y text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s10853-006-0601-y text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Alves C. Complex Fluid Group, Instituto de Física, Universidade de Brasília, CP 04455, 70919-970, Brasília, DF, Brazil aut NATIONALLICENCE 700 1- Aquino Renata Complex Fluid Group, Instituto de Física, Universidade de Brasília, CP 04455, 70919-970, Brasília, DF, Brazil aut NATIONALLICENCE 700 1- Depeyrot Jérôme Complex Fluid Group, Instituto de Física, Universidade de Brasília, CP 04455, 70919-970, Brasília, DF, Brazil aut NATIONALLICENCE 700 1- Tourinho Francisco Complex Fluid Group, Instituto de Química, Universidade de Brasília, CP 04478, 70919-970, Brasília, DF, Brazil aut NATIONALLICENCE 700 1- Dubois Emmanuelle Laboratoire des Liquides Ioniques et Interfaces Chargées, Université Pierre et Marie Curie, Bât. F, Case 63, 4 place Jussieu, 75252, Paris Cedex 05, France aut NATIONALLICENCE 700 1- Perzynski Régine Laboratoire des Liquides Ioniques et Interfaces Chargées, Université Pierre et Marie Curie, Bât. F, Case 63, 4 place Jussieu, 75252, Paris Cedex 05, France aut NATIONALLICENCE 773 0- Journal of Materials Science Kluwer Academic Publishers-Plenum Publishers; http://www.springer-ny.com 42/7(2007-04-01), 2297-2303 0022-2461 42:7<2297 2007 42 10853 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer