Volume 91, Issue 10, 15 May 2002
Index of content:
- MAGNETIC FLUIDS, BIOMAGNETISM, AND MAGNETOCHEMISTRY
91(2002); http://dx.doi.org/10.1063/1.1452205View Description Hide Description
In order to clarify whether or not there is any magnetic interaction between the magnetic colloidal particles in magnetic fluids (MFs), we present a method for comparing the magnetization curve of a mother MF with that of a few-thousand-fold diluted solution. For a MF which showed clusters of colloidal particles in an optical microscope under an applied magnetic field, the hysteresis loops for the mother MF and its few-thousand-fold dilution displayed different shapes for weak fields. We conclude from this result that strong magnetic interactions exist between the particles in this MF. On the contrary for a MF which showed no clusters under optical microscopy, no differences in shapes of the hysteresis loops for the mother MF and its few-thousand-fold dilution were observed in the weak field region. However, differences were observed for the field region above 80 kA/m.
91(2002); http://dx.doi.org/10.1063/1.1452206View Description Hide Description
Magnetic nanowires suspended in fluid solutions can be assembled and ordered by taking advantage of their large shape anisotropy. Magnetic manipulation and assembly techniques are demonstrated, using electrodepositedNinanowires, with diameter 350 nm and length 12 μm. Orienting suspended nanowires in a small magnetic field promotes self-assembly of continuous chains that can extend over several hundred μm. The dynamics of this process can be described quantitatively in terms of the interplay of magnetic forces and fluid drag at low Reynolds number. In addition, a new technique of magnetic trapping is described, by which a single magnetic nanowire can be captured between lithographically patterned magnetic microelectrodes. The use of three-segment Pt–Ni–Pt nanowires yields low resistance, Ohmic electrical contacts between the nanowires and the electrodes. This technique has potential for use in the fabrication and measurement of nanoscale magnetic devices.
91(2002); http://dx.doi.org/10.1063/1.1453951View Description Hide Description
Dipole approximations are used to model up to three superparamagnetic particle systems as they assemble on magnetic island templates. It is shown that small variations in the ratio of particle-to-island diameter as well as the particle positions above the island can change magnetic forces from attractive to repulsive. This observation could potentially permit a template to be designed to promote single particle coverage of individual magnetic islands.
91(2002); http://dx.doi.org/10.1063/1.1452207View Description Hide Description
Trypsin, a proteolytic enzyme or a protein, was immobilized onto the surfaces of ferrite mixed solution) fine particles, ∼8 nm in size, during the process in which the particles were synthesized from an aqueous solution. The process was performed in the open air at a temperature as low as 4 °C and on near-neutral condition of which is compatible with most of the bioactive molecules as well as trypsin. Therefore this technique is advantageous for preparing magnetite particles having biomolecules immobilized on their surfaces, which will be used for biomedical applications utilizing magnetic separation technique.
91(2002); http://dx.doi.org/10.1063/1.1447522View Description Hide Description
The effect of a magnetic field on the electrode potential of Fe, Co, Ni, and Cu in different electrolytes was investigated. The electrolytes used were iron(III) chloride (0.02–0.6 M/l), iron (III) nitrate (0.06 M/l), caustic soda (8 M/l), hydrochloric acid (0.1 M), and sulphuric acid (0.1 M). All measurements were made at room temperature in magnetic fields of up to 4 kOe. Results from experiments with nickel and cobalt ferromagneticelectrodes and different electrolytes showed no effect of magnetic field. On the contrary, magnetic field caused a proportional change in the potential of the ferromagneticironelectrode in solutions of iron(III) chloride and nitrate, and caustic soda. A significant long-time drift of the potential was found in all electrolytes. The electrode magnetization change gives the change of the potential, which is not proportional to magnetization.