Magnetic interactions between nanoparticles

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

Beilstein J. Nanotechnol. 2010, 1, 182–190, doi:10.3762/bjnano.1.22

• 10.3762/bjnano.1.22 Abstract We present a short overview of the influence of inter-particle interactions on the properties of magnetic nanoparticles. Strong magnetic dipole interactions between ferromagnetic or ferrimagnetic particles, that would be superparamagnetic if isolated, can result in a

• collective state of nanoparticles. This collective state has many similarities to spin-glasses. In samples of aggregated magnetic nanoparticles, exchange interactions are often important and this can also lead to a strong suppression of superparamagnetic relaxation. The temperature dependence of the order

• ferrimagnetic Fe3O4 layers with a Curie temperature of about 850 K. Similarly, an increase of the Curie temperature of ferrimagnetic γ-Mn2O3 due to interaction with antiferromagnetic MnO has been found in MnO/γ-Mn2O3 core–shell particles [6]. The magnetic properties of non-interacting magnetic nanoparticles are

Magnetic nanoparticles for biomedical NMR-based diagnostics

• Huilin Shao,
• Tae-Jong Yoon,
• Monty Liong,
• Ralph Weissleder and
• Hakho Lee

Beilstein J. Nanotechnol. 2010, 1, 142–154, doi:10.3762/bjnano.1.17

• medicine. In general, biological samples have only negligible magnetic susceptibility. Thus, using magnetic nanoparticles for biosensing not only enhances sensitivity but also effectively reduces sample preparation needs. This review focuses on the use of magnetic nanoparticles for in vitro detection of

• biomolecules and cells based on magnetic resonance effects. This detection platform, termed diagnostic magnetic resonance (DMR), exploits magnetic nanoparticles as proximity sensors, which modulate the spin–spin relaxation time of water molecules surrounding molecularly-targeted nanoparticles. By developing

• more effective magnetic nanoparticle biosensors, DMR detection limits for various target moieties have been considerably improved over the last few years. Already, a library of magnetic nanoparticles has been developed, in which a wide range of targets, including DNA/mRNA, proteins, small molecules

Review and outlook: from single nanoparticles to self-assembled monolayers and granular GMR sensors

• Alexander Weddemann,
• Inga Ennen,
• Anna Regtmeier,
• Camelia Albon,
• Annalena Wolff,
• Katrin Eckstädt,
• Nadine Mill,
• Michael K.-H. Peter,
• Jochen Mattay,
• Carolin Plattner,
• Norbert Sewald and
• Andreas Hütten

Beilstein J. Nanotechnol. 2010, 1, 75–93, doi:10.3762/bjnano.1.10

• interactions is discussed. Keywords: bottom-up particle synthesis; dipolar particle coupling; granular giant magnetoresistance sensor; magnetic nanoparticles; self-assembly; Introduction Magnetic nanoparticles have been thoroughly studied during the last decades due to their many promising applications in

• monitoring of magnetically labeled biomolecules. The interaction between several particles is also of high practical relevance: Due to different types of coupling, magnetic nanoparticles assemble in superstructures. Various technological applications such as their employment in data storage devices, where

• degrees of freedom. Within such assemblies, magnetic nanoparticles themselves may act as magnetoresistive sensor devices: Surrounded by a non-magnetic matrix, various spin-dependent transport phenomena have been observed [5][6][7][8][9]. Contrary to formerly used metallurgic preparation techniques

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

• the magnetization and the magnetic hyperfine field, in contrast to the Bloch T3/2 law in bulk materials. The temperature dependence of the average magnetization is conveniently studied by Mössbauer spectroscopy. The energy of the uniform excitations of magnetic nanoparticles can be studied by

• inelastic neutron scattering. Keywords: collective magnetic excitations; Mössbauer spectroscopy; neutron scattering; spin waves; superparamagnetic relaxation; Review Introduction One of the most important differences between magnetic nanoparticles and the corresponding bulk materials is that the magnetic

• these effects may be difficult to distinguish from the contribution from the thermoinduced magnetization. Conclusion After the discovery of superparamagnetism much of the research in the field of magnetic nanoparticles has focused on superparamagnetic relaxation while the magnetic dynamics below TB has

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

• conservation of nanoparticles by Au photoseeding is presented. Keywords: Co; CoPt; core–shell particles; FePt; magnetic anisotropy; magnetic particles; plasma etching; reverse micelles; self-assembly; Introduction Magnetic nanoparticles have been the focus of research for over 60 years [1][2]. These

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

• magnetic NPs, which are in the focus of the present Thematic Series entitled “Preparation, properties and applications of magnetic nanoparticles”. While the most notable feature of magnetic NPs, their superparamagnetic behavior, has already been reported by Neel as early as 1949 [6], this phenomenon