Magnetic properties of acicular ultrafine iron particles

Magnetic properties of acicular (similar to60 and similar to200 nm) iron particles, obtained by reduction of alumina-coated goethite particles, are reported. X-ray diffraction and Mossbauer spectroscopy showed that the particles consist of a alpha-Fe core and a thin surface layer of maghemite. Magnetization data indicated an improvement of similar to28% in the saturation magnetization, coercive field, and squareness for particles with similar to60 nm. This magnetic property enhancement of the present particles, whose size is 40% smaller than those commercially available, could result in a similar decrease of the bit-size for higher density of magnetic media

Contactless magnetoresistance studies of Co/Cu multilayers using the infrared magnetorefractive effect

The magnetotransport properties of giant magnetoresistive Co∕Cu multilayers are studied with the magnetorefractive effect: a noncontact technique, which uses infrared electromagnetic radiation. Four Co∕Cu samples were analyzed with the structure (Co15.5 Å∕Cux)25 which exhibit magnetoresistance values from 1.9 to 65 %. The magnetorefractive curves were modeled using the complex dielectric function as derived by Jacquet and Valet [J. C. Jacquet and T. Valet, Magnetic Ultrathin Films, Multilayer and Surfaces, edited by E. Marinero (Materials Research Society, Pittsburgh, 1995)]. The shape and magnitude of the curves were found to be very sensitive to the interface scattering lifetime. This classical model is successful in simulating the long wavelength behavior, but is not able to reproduce the correct shape or sign at short wavelengths where the band structure of the materials becomes important. The good agreement at long wavelengths between electrical magnetotransport measurements and the noncontact magnetorefractive effect demonstrates the possibilities of using infrared reflection spectroscopy for the characterization of giant magnetoresistive systems