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peer-reviewed The effect of Fe, Cu, Zr, and Ti substitution on magnetic properties of SmCo 1:7 magnets at temperatures up to 500°C were studied. As-milled amorphous Sm(Co,Fe,Cu,Ti-Zr)7 magnets crystallized in the TbCu7-type structure after annealing at 750°C for 2 h. A room-temperature intrinsic coercivity of around 2.5 T is obtained for compositions SmCo6.4 Zr0.2 Ti0.4 and SmCo6.4 Fe0.1 Zr0.1 Ti0.4. The high coercivity of the ball-milled SmCo7-x Tix magnets is attributed to the strong pinning of the walls of the "interaction domains" by the network of grain boundaries between the nanocrystalline grains. The virgin curve of the ball-milled samples is suggestive of strong domain wall pinning.

peer-reviewed We report the preparation, characterization of structure and magnetic properties of electrodeposited L1 0 FePt films with high coercivity. Equiatomic as-deposited films are nanocrystalline, soft and magnetically isotropic. The transition from the disordered to the ordered phase was studied by varying the annealing time and annealing temperature. The as-deposited nanocrystalline deposits were treated in forming gas and developed the tetragonal L1 0 structure only at temperatures above 500 ºC. The coercivity increases with both annealing temperature and time reaching a value of 1.5 T at 900 ºC. The magnetization reversal mechanism was identified as nucleation type from the initial magnetization curve of a thermally demagnetised sample. SFI MANSE project

The ability of living cells, either adherent or suspended, to internalize nickel nanowires is demonstrated for MC3T3-E1, UMR106-tumour and Marrow-Stromal cells. Nanowires were produced by electrodeposition, 20 μm long and 200 nm in diameter. Cell separation and manipulation was achieved for the three cell types. Applied magnetic field successfully oriented the internalized nanowires but no clear anisotropy is induced on the adherent cells. Nanowires tend to bind to cytoplasm metalloproteins and trigger lysosome reorganization around the nucleus. This work demonstrates the applications of nanowires in adherent and suspended cells for cell separation and manipulation, and further explore into their role in nanobiotechnology.

PUBLISHED, High temperature ferromagnetism in thin films of dilute magnetic oxides is a widespread phenomenon, of which there appear to be two sources. One is the contribution of the 3d dopant ions themselves, the other is related to crystal defects in the interface region. The latter contributes a magnetic moment of 100?400??B per square nanometer of substrate area, which is largely independent of film thickness or dopant concentration. It is suggested that the defects are two-electron or two-hole centers which have a spin triplet as ground state or low-lying excited state. HfO2, an example of the former, is ferromagnetic even when undoped. In ZnO or SnO2, examples of the latter, the magnetic dopant may stabilize the spin triplet by exchange., This work was supported by Science Foundation Ireland, as part of the CINSE Project. The author is grateful to many coworkers, including L. S. Dorneles, C. B. Fitzgerald, R. Gunning, J. G. Lunney, M. Moliner, P. Stamenov, M. Venkatesan, and Y. Zhou. M. Konno of Hitachi Science Systems Ltd. kindly took the STEM image.

PUBLISHED, We report on field annealing effects in spin valves with an IrMn pinning layer and spin valves with a synthetic antiferromagnet. The exchange bias field and magnetoresistance of spin valves with an IrMn/CoFe bilayer at the bottom improve drastically upon annealing in large magnetic fields. The evolution of the exchange bias field with annealing field strength shows a rapid increase up to an applied field of 0.5 T, which is followed by a more gradual improvement up to an annealing field of 5.5 T. The increase of the exchange bias field in large magnetic fields indicates that the interfacial spin structure of the IrMn layer is directly influenced by the annealing field strength., The authors wish to acknowledge M. Venkatesan for SQUID measurements. This work was supported by Science Foundation Ireland as part of the CINSE program.

PUBLISHED, We report on cylindrical permanent-magnet structures that exploit the image effect in a surrounding circular soft-iron sheath. We present the theory for a general multipole ring, where the polarization direction ? = (n + 1)?, n is a positive or negative integer, and ? is the angular coordinate. For the uniformly magnetized case n = -1, a long cylindrical ring produces no field in its bore, and the field outside the cylinder is that of a linear dipole. When surrounded by the sheath, the field becomes uniform in the bore and zero outside the cylinder. Higher multipole fields can similarly be transformed from outward fields to inward fields by using the sheath. The field can be varied continuously by moving the sheath. We describe a small variable-field device using a Nd-Fe-B cylinder that produces a flux density of 0-400 mT., The authors wish to thank M. O'Reilly for the mechanical work and R. Gunning for help with the diagrams.

peer-reviewed This work focuses on a search for magnets that can be used at elevated temperature. We have studied the effect of ZrB2 addition on the magnetic properties and stability of nanocrystalline 1:7 type Sm(Co,Ti,Zr) magnets up to 500??C. Amorphous ball milled powder was annealed to develop the TbCu7 type structure. The room temperature coercivity of SmCo6.5(ZrB2)0.033Ti0.4 is 2.1 T. The microstructure is stable at 400??C, where the coercivity is 0.5T.

PUBLISHED, The application of a magnetic field unexpectedly alters the rest potential of ferromagnetic electrodes in paramagnetic solutions of their salts. Anodic shifts of up to 60 mV in a field of 1 tesla were observed for 1Miron electrodes in iron nitrate solution. The magnitude of the shift depends on magnetic field strength and orientation and it varies with the anion used. The shift is smaller for cobalt and nickel ( 2 mV) than for iron. The effect is attributed to modifications in the rate of mass transport under the influence of the magnetic field gradient force.

peer-reviewed A novel method of producing magnetoresistive oxides is described, which involves low temperature combustion synthesis from a mixture of nitrates and fuel, as applied to Sr2FeMoO6. The method yields ceramics with a fine crystallite size of 100???200 nm and a room temperature resistivity of 200 mV m. Low field magnetoresistance (6.5% in 0.1 T) is enhanced dramatically compared to samples prepared by conventional solid-state reaction due to the efficient intergrain tunnelling arising from the high density of grain boundaries. Magnetoresistance in low fields is essentially independent of temperature from 5???300 K, and it persists up to 350 K, providing the prospect of sensor applications in an extended temperature range.

PUBLISHED, The conductivity of a nanocontact between two crystallites of magnetite (Fe3O4) was studied. It was found that the conductivity can increase sixfold at room temperature in an applied field of 7 mT (70 Oe). This large low-field effect was attributed to spin-polarized electrons hopping across a very narrow domain wall at the contact. Spin pressure on the domain wall at the nanocontact led to nonlinearity of the I(V) characteristic, and the possibility of fast switching in a bistable two- or three-terminal device via current-induced wall motion., This work was supported by the EU as part of the AMORE project in the growth program, and by Enterprise Ireland under Contract No. SC/99/225.

PUBLISHED