https://doi.org/10.1140/epjb/e2008-00294-6
Effective anisotropy field variation of magnetite nanoparticles with size reduction
1
Centro Atómico Bariloche and Instituto
Balseiro, 8400 S. C. de Bariloche, RN, Argentina
2
Instituto de Física “Gleb Wataghin”, Universidade Estadual de Campinas, Campinas (SP) 13081-970, Brazil
Corresponding author: a vargasjm@ifi.unicamp.br
Received:
28
February
2008
Revised:
9
June
2008
Published online:
25
July
2008
Size effect on the internal magnetic structure has been
investigated on weakly interacting magnetite (Fe3O4)
nanoparticles by ferromagnetic resonance experiments at 9.5 GHz as
a function of temperature (4–300 K).
A set of three samples with mean particle size of 2.5 nm, 5.0 nm
and 13.0 nm, respectively, were prepared by chemical route with
narrow size distribution (). To minimize the dipolar
interaction, the particles were dispersed in a liquid and a solid
polymer matrix at ~0.6% in mass.
By freezing the liquid suspension with an applied external field,
a textured was obtained. Thus, both random and textured
suspensions were studied and compared.
The ferromagnetic resonance experiments in zero-field-cooled and
field-cooled conditions were carried out to study the size effect
on the effective anisotropy field.
The dc magnetization measurements clearly show that the
internal magnetic structure was strongly affected by the particle
size.
PACS: 75.50.Tt – Fine-particle systems; nanocrystalline materials / 75.30.Gw – Magnetic anisotropy / 75.60.Ch – Domain walls and domain structure / 76.50.+g – Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2008