Superparamagnetic properties

More recently, electrostatic adsorption of Fe304 nanoparticles has been reported, showing superparamagnetism properties for the system [225]. 

The superparamagnetic properties of -Fe203 have also been studied via the Mossbauer effect. Nakamura et al, (32) have investigated the temperature dependence of the internal field in -Fe203 particles of approximately 50 A. diameter. At 120 °K. they obtain a spectrum which is almost identical to the bulk material, except that no Morin transition has occurred and the spins still lie in the basal plane. At room temperature the magnetic hyperfine spectrum collapses (even though the bulk... 

Pemet, M. Obrados, X. Fontcuberta, J. Joubert, J.C. Tejada, J. (1984) Magnetic structure and superparamagnetic properties of 5-FeOOH. IEEE Trans. Magn. Mag. 20 1524-1526... 

Nonspherical, surface-imprinted magnetic PMMA (see Fig. 28) nanoparticles could be prepared by Tan et al. [177, 178]. A miniemulsion process was used to prepare magnetite/PMMA nanoparticles on which proteins were either immobilized by adsorption (RNAse A) [178] or covalently (bovine serum albumin, BSA) [177]. After creating a shell of PMMA, the proteins were removed, leaving cavities on the particles surface. The BSA-imprinted nanoparticles showed superparamagnetic properties and exhibited a high rebinding capacity for BSA. 

Chen, Q., Zhang, Z.J. Size-dependent superparamagnetic properties of MgFe204 spinel ferrite nanocrystallites. Appl. Phys. Lett. 73, 3156-3158 (1998)... 

Liu, C., Rondinone, A.J., Zhang, Z.J. Synthesis of magnetic spinel ferrite CoFc204 nanoparticles from ferric salt and characterization of the size-dependent superparamagnetic properties. Pure Appl. Chem. 72, 37-45 (2000)... 

C. Liu and Z. J. Zhang, Size-dependent superparamagnetic properties of Mn spinel ferrite... 

Tan ST, Wcndorff JH, Pictzonka C, Jia ZH, Wang GQ (2005) Biocompatible and biodegradable polymer nanofibers displaying superparamagnetic properties. ChemPhysChem 6 1461-1465... 

One of the issues in the practical application of nanostructured materials is the ability to synthesize sufficient quantities with appropriate and controllable properties at low cost. Gas phase combustion processes provide one of the best methods for the bulk production of nanostructured materials due to the relative ease of scale-up and the relative simplicity of the process. The magnetic system chosen for study was y-Fc203/Si02 because a composite of this class has been demonstrated to yield superparamagnetic properties (3) via a liquid phase synthesis route. 

In this paper we have demonstrated the application of gas-phase combustion processes to produce nanocomposites with superparamagnetic properties. The combustion process was designed in such a way as to allow for the rapid formation of nano-liquid droplets which would phase segregate, combined with rapid quenching to preserve the microstructure and chemical composition. The resulting material showed superparamagnetic behavior between 155 K and room temperature. 

The core-shell magnetic particles present superparamagnetic properties and their saturation magnetization values are correlated with those reported by the literature. 

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