LA DANSE DES FERROFLUIDES - Sciences à l'Ecole

JOURNAL OF APPLIED PHYSICS 105, 023911 (2009)
Magnetic hyperthermia in single-domain monodisperse
FeCo nanoparticles:
Evidences for Stoner–Wohlfarth behavior and large
losses
Donc, en français, quand le champ magnétique appliqué est faible par rapport au champ
maximal des nanoparticules, la théorie de la réponse linéaire peut être utilisée, dans ce cas la
boucle d’hystérésis s’apparente à une ellipse dont la formule de l’aire est ci-dessus.
« However the linear theory is inappropriate for ferromagnetic NPs or for NPs close to the
superparamagnetic/ferromagnetic transition, since the applied magnetic field can be close to the
saturation field. In the ferromagnetic state, the SW model is more suitable to interpret the
experimental data. »
« For randomly oriented uniaxial NPs, this area is A=αμ0MSHC0, where α=2 and HC0 is the value of
the coercive field HC at T=0. »
« particles should be single domain and rather monodisperse to avoid convolution effects or the
presence of too many multidomain NPs, they should have a small enough coercive field even at high
frequency so that a moderate magnetic
field can saturate their magnetization, and measurements should be
performed on systems where dipolar interactions do not influence the
NP intrinsic magnetic properties too much. The meeting of these
three requirements at the same time is not trivial. Especially, in the
size range of interest 10–40 nm, many synthesis methods fail in
reaching a narrow size distribution. This may explain why, so far,
experimental evidences for SW behavior in hyperthermia
measurements have never been reported. »
JOURNAL OF APPLIED PHYSICS 105, 023911 (2009)
Magnetic hyperthermia in single-domain monodisperse FeCo
nanoparticles:
Evidences for Stoner–Wohlfarth behavior and large losses
L’article montre d’abord que la théorie linéaire convient pour
des nanoparticules qui ne nous intéressent pas, le modèle SW
convient mieux pour évaluer un A important, pour des
particules intéressantes pouvant produire un fort
échauffement.
La danse du ferrofluides 27