A single domain ferromagnetic particle is characterized by an internal potential, having several local states of equilibrium with potential barriers between them. If the particles are small ~; 10 nm! so that the potential barriers are relatively low, the magnetization vector M may cross over the barriers due to thermal agitation. The ensuing thermal instability of the magnetization results in t...

In order to prominently investigate the effects of the surface spin on the magnetic properties, the weak magnetic ZnLa0.02Fe1.98O4 nanoparticles were chosen as studying objects which benefit to reduce as possibly the effects of interparticle dipolar interaction and crystalline anisotropy energies. By annealing the undiluted and diluted ZnLa0.02Fe1.98O4 nanoparticles at different temperatures, w...

Magnetic granular solids consist of nanometer-sized magnetic particles uniformly dispersed and embedded in an immiscible insulating or metallic medium. They display a rich variety of magnetic properties and giant magneto-transport properties due to their unique nanostructure, which can be usefully described by the metal volume fraction and the metal particle diameter of granular solids. Fabrica...

Insulating compounds of the magnetic dilution series Eu Sr, S reveal spin glass behavior for 0.13^ x £ 0.65, similar to that in metallic alloy's*. :-7e discuss some of the experimental properties characterizing both the spin-glass state and the nature of the transition. A microscopic picture of the "frozen" state is presented based on the competition of ferromagnetic nearest neighbor and antife...

We first demonstrate a simple "one-pot" method to synthesis uniform Fe3O4 hollow microspheres in the presence of PEG in ethylene glycol by using urea to control their morphologies. The interior cavity of the hollow spheres can be tunable by reaction time. The Lamer model was used to explain the formation of magnetite hollow spherical structures based on the experimental observations. The obtain...

This chapter provides an introduction to the fundamental physical ideas and models relevant to the phenomenon of magnetic hysteresis in nanoparticle assemblies. The concepts of single-domain particles and superparamagnetism are discussed. The mechanisms of magnetization by coherent rotation and the role of temperature in the gradual decay of magnetization are analyzed in the framework of simple...

We report a facile intracellular manipulation of fluorescent magnetic Fe3O4-CdSe nanoparticles using magnetic force. The growth of CdSe quantum dots on Fe3O4 nanoparticles produces Fe3O4-CdSe nanoparticles with two distinct properties, fluorescence and superparamagnetism. After nonspecific surface modification using glutathione (GSH), the hydrophilic Fe3O4-CdSe@GSH nanoparticles can be easily u...

We report on the Fe17 high-spin molecular cluster and show that this system is an exemplification of nanostructured dipolar magnetism. Each Fe17 molecule, with spin S=35/2 and axial anisotropy as small as D approximately -0.02 K, is the magnetic unit that can be chemically arranged in different packing crystals while preserving both the spin ground state and anisotropy. For every configuration,...