Two-step single-reactor synthesis of oleic acid- or undecylenic acid-stabilized magnetic nanoparticles by thermal decomposition

• Mykhailo Nahorniak,
• Pamela Pasetto,
• Jean-Marc Greneche,
• Volodymyr Samaryk,
• Sandy Auguste,
• Anthony Rousseau,
• Nataliya Nosova and
• Serhii Varvarenko

Beilstein J. Nanotechnol. 2023, 14, 11–22, doi:10.3762/bjnano.14.2

• typical for the presence of superparamagnetic relaxation phenomena suggested a very small size (about 10 nm compared to results from the literature) for the synthesized nanoparticles, which was consistent with electron and XRD diffraction results, as well as TEM results. Different fitting models can be

• sample. The shape of a single line at 300 K and a more pronounced ultrafine structure at 77 K indicate a decrease in superparamagnetic relaxation phenomena, probably caused by a larger size of the nanoparticles. Furthermore, the spectrum recorded at 77 K can be divided into four different components: (i

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

• 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

• : dipole interactions; exchange interactions; spin structure; superferromagnetism; superparamagnetic relaxation; Review Introduction In nanostructured magnetic materials, interactions between, for example, nanoparticles or thin films in multilayer structures often play an important role. Long-range

• often strongly influenced by superparamagnetic relaxation at finite temperatures. For a nanoparticle with uniaxial anisotropy and with the magnetic anisotropy energy given by the simple expression there are energy minima at θ = 0° and θ = 180°, which are separated by an energy barrier KV. Here K is the

Ultrafine metallic Fe nanoparticles: synthesis, structure and magnetism

• Olivier Margeat,
• Marc Respaud,
• Catherine Amiens,
• Pierre Lecante and
• Bruno Chaudret

Beilstein J. Nanotechnol. 2010, 1, 108–118, doi:10.3762/bjnano.1.13

• Mössbauer spectroscopy, τm is in the range of 10−8 s [33][34][35] and the superparamagnetic relaxation time is given by where ν is the volume, Keff the effective anisotropy, and τ0 is of the order of 10−11–10−9 s [36]. The blocking temperature of the material corresponds to the temperature where the blocked

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

• 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

• dynamics differ substantially. The magnetic anisotropy energy of a particle is proportional to the volume. For very small particles at finite temperatures it may therefore be comparable to the thermal energy. This results in superparamagnetic relaxation, i.e., thermally induced reversals of the

• magnetization direction. For a particle with a uniaxial anisotropy energy E(θ) given by the simple expression in Equation 1, the superparamagnetic relaxation time τ is given by Equation 2 [1][2]. Here K is the magnetic anisotropy constant, V is the particle volume, θ is the angle between an easy axis and the