Uniform excitations in magnetic nanoparticles

• Steen Mørup,
• Cathrine Frandsen and
• Mikkel Fougt Hansen

Beilstein J. Nanotechnol. 2010, 1, 48–54, doi:10.3762/bjnano.1.6

• classical magnetic moment, i.e., it is assumed that the magnetization vector can point in any direction [3][4][5]. Below TB, the magnetization direction remains near one of the minima and the temperature dependence of the magnetization can be calculated by use of Boltzmann statistics: where E(θ) is given by

• nanoparticles (Figure 4). The energy of the uniform excitations in antiferromagnetic materials, Equation 16, was derived assuming that the antiferromagnetic material had zero net magnetization, but nanoparticles of antiferromagnetic materials usually have a magnetic moment because of uncompensated spins, for

• example, in the surface [23][26]. This can have a large influence on the excitation energy [25][27]. For example, an uncompensated magnetic moment of only around 1% of the sublattice magnetic moment can result in a decrease of the excitation energy by a factor of two [27]. Neutron studies of hematite

Preparation and characterization of supported magnetic nanoparticles prepared by reverse micelles

• Ulf Wiedwald,
• Luyang Han,
• Johannes Biskupek,
• Ute Kaiser and
• Paul Ziemann

Beilstein J. Nanotechnol. 2010, 1, 24–47, doi:10.3762/bjnano.1.5

• interparticle distances of 100 nm on a 5 × 5 mm2 substrate produce a total magnetic moment of only 10–9 Am2 (10–6 emu). Although state-of-the-art SQUID-magnetometry is able to detect the related small signals, the response of the diamagnetic substrate has to be taken into account as well delivering for the

• the saturation moment with the considerations mentioned above, we expected a total sample magnetic moment of 2.8∙10–9 Am2 (2.8∙10–6 emu) taking into account the NPs density at an average distance of 60 nm. Although this estimate is 44% lower than the experimental value, this deviation is acceptable

Preparation, properties and applications of magnetic nanoparticles

• Ulf Wiedwald and
• Paul Ziemann

Beilstein J. Nanotechnol. 2010, 1, 21–23, doi:10.3762/bjnano.1.4

• scale of typically a decade is not at all compatible with superparamagnetism. A natural way out of this problem is to look for materials exhibiting an as high as possible magnetocrystalline anisotropy which suppresses fluctuations of the effective magnetic moment of the NPs [7]. For binary alloys like