The Role of Interactions in Systems of Single Domain Ferrimagnetic Iron Oxide Nanoparticles

Magnetic nanoparticles are interesting materials for a lot of medical and technical applications. A less experimentally investigated question is the influence of particle packing density on magnetic properties due to magnetic interactions between single particles. For this, magnetic nanoparticles of iron oxides prepared as fine dry powder by laser deposition are investigated with respect to their structural and magnetic properties as function of packing density. The particles are nearly spherically shaped single crystals in the magnetic single domain size range with a mean diameter of 21 nm occasionally exhibiting spinel growth facets. Powders of these particles are diluted by nonmagnetic silicon oxide particles in a range of volume concentrations from 0.2 % up to 68 % of the bulk density of magnetite. The concentration dependence of remanence, coercivity and hysteresis losses is determined by measurements of minor loops in a vibrating sample magnetometer. Results which are discussed in the frame of present theoretical models may be understood in terms of the cubic anisotropy of magnetite distorted by a small uniaxial shape contribution. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2778

Magnetic particle hyperthermia: nanoparticle magnetism and materials development for cancer therapy

Loss processes in magnetic nanoparticles are discussed with respect to optimization of the specific loss power (SLP) for application in tumour hyperthermia. Several types of magnetic iron oxide nanoparticles representative for different preparation methods (wet chemical precipitation, grinding, bacterial synthesis, magnetic size fractionation) are the subject of a comparative study of structural and magnetic properties. Since the specific loss power useful for hyperthermia is restricted by serious limitations of the alternating field amplitude and frequency, the effects of the latter are investigated experimentally in detail. The dependence of the SLP on the mean particle size is studied over a broad size range from superparamagnetic up to multidomain particles, and guidelines for achieving large SLP under the constraints valid for the field parameters are derived. Particles with the mean size of 18 nm having a narrow size distribution proved particularly useful. In particular, very high heating power may be delivered by bacterial magnetosomes, the best sample of which showed nearly 1 kW g−1 at 410 kHz and 10 kA m−1. This value may even be exceeded by metallic magnetic particles, as indicated by measurements on cobalt particles

Growth Kinetics and Some Properties of Thick LPE YIG Layers

Three high temperature solutions (HTS) with liquidus temperatures T L = 876°C(1), 980°C(2), and 1005°C (3) were used for the deposition of thick Y 3-uPb uFe 5-tPt tO 12 layers on 20 mm and 50 mm diameter 111 Gd 3Ga 5O 12 substrates and of thin layers on slightly spherically shaped 110 and 211 substrates. The transport resistance δ/D of HTS 1 is larger by a factor 1.8 and the interfacial resistance 1/k by a factor 6.5 compared with those of HTS 3. The kinetic coefficients k st of steps of HTS 1 and those of HTS 2 and HTS 3 differ by about an order of magnitude. Characterization of 111 thick layers is carried out with respect to composition, misfit, magnetic saturation polarization, Curie temperature, and ferromagnetic resonance linewidth. © 1988

Optimization of Flux Composition for Thick YIG Layers

Thick, nominally pure (only lead substituted) Y 3Fe 5O 12 (YIG) films have been grown on gadolinium gallium garnet (GGG) substrates 2 inches in diameter by isothermal dipping method of liquid phase epitaxy from lead-borate melt. If the liquidus temperature of the melt and the supercooling are varied over in a wide range, 1151-1319 K and 10-48 K, respectively, and one examines the supercoolability of the melt, the lattice parameter, Pb content, FMR linewidth and the surface quality of the prepared layer it can be stated that nominally pure YIG layer on GGG substrate 50 mm in diameter can be grown by only one dipping step up to about 80 μm in thickness without surface defects. © 1987 Akadémiai Kiadó

Towards nanomedicines of the future: Remote magneto-mechanical actuation of nanomedicines by alternating magnetic fields

The paper describes the concept of magneto-mechanical actuation of single-domain magnetic nanoparticles (MNPs) in super-low and low frequency alternating magnetic fields (AMFs) and its possible use for remote control of nanomedicines and drug delivery systems. The applications of this approach for remote actuation of drug release as well as effects on biomacromolecules, biomembranes, subcellular structures and cells are discussed in comparison to conventional strategies employing magnetic hyperthermia in a radio frequency (RF) AMF. Several quantitative models describing interaction of functionalized MNPs with single macromolecules, lipid membranes, and proteins (e.g. cell membrane receptors, ion channels) are presented. The optimal characteristics of the MNPs and an AMF for effective magneto-mechanical actuation of single molecule responses in biological and bio-inspired systems are discussed. Altogether, the described studies and phenomena offer opportunities for the development of novel therapeutics both alone and in combination with magnetic hyperthermia