Superparamagnetic blocking of an ensemble of magnetite nanoparticles upon interparticle interactions

• Published in: Journal of magnetism and magnetic materials Vol. 440; pp. 199 - 202
• Main Authors: Balaev, D.A., Semenov, S.V., Dubrovskiy, A.A., Yakushkin, S.S., Kirillov, V.L., Martyanov, O.N.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.10.2017; Elsevier BV
• Subjects: Anisotropy; Blocking temperature; Diamagnetism; Dispersions; Fe3O4 nanoparticles; Iron oxides; Magnetic anisotropy; Magnetic dipoles; Magnetic fields; Magnetic properties; Magnetite; Nanoparticles; Parameter estimation; Size effect; Superparamagnetic nanoparticles; Superparamagnetic nanoparticles; Blocking temperature; Fe3O4 nanoparticles; Size effect
• ISSN: 0304-8853; 1873-4766
• DOI: 10.1016/j.jmmm.2016.12.046

We report on the effect of interparticle magnetic interactions in an ensemble of superparamagnetic magnetite particles with an average size of ~8.4nm dispersed in the diamagnetic matrix on the blocking of this ensemble in external magnetic field. The two limit cases are investigated: the case of strongly interacting particles, when the value of magnetic dipole-dipole interaction between particles is comparable with the energy of other interactions in the ensemble (the interparticle distance is similar to the nanoparticle diameter) and the case of almost noninteracting particles distant from each other by about ten particle diameters. We demonstrate that the experimental dependence of the blocking temperature on external field is described well within the model [1], in which the density of particles in a nonmagnetic medium is taken into account and the correlation value depends on external magnetic field. The model for describing the magnetic properties of a disperse nanoparticle ensemble is proposed, which makes corrections related to the particle size and mean dipole-dipole interaction energy for the anisotropy constant. The surface magnetic anisotropy of Fe3O4 particles and parameters of the interparticle coupling are estimated. •The interparticle interactions affect superparamagnetic behavior of nanoparticles;•Effective magnetic anisotropy constant depends on interparticle interaction energy;•Modified random anisotropy model was used for 3-D dispersed nanoparticles ensemble.