Giant magnetoresistance in melt-spun metallic ribbons

Granular Cu-Co alloys as interacting superparamagnets

“…Even a random anisotropy model, recently applied to describe hysteretic features of these systems, 28 cannot be invoked to explain the origin and temperature evolution of the apparent moment. 29 Quite interestingly, very similar results were found at much lower temperatures in other Cu-Co granular ribbons by Dieny et al; 25 in some cases, the reduced magnetization was found to scale with M S (H/T) only above 50 K, while below that temperature all M /M S vs H curves were found to overlap-this is equivalent to a scaling law of the H/M S type, because the saturation magnetization is constant at low T. Such a behavior, observed also in more concentrated Cu-Co alloys over an extended temperature interval, was generically related to the effects of single-particle blocking and of random, collective interactions among particles. 25 The puzzling behavior of the anhysteretic magnetization deserves a more systematic study.…”

“…Bulk granular alloys are usually described as superparamagnetic ͑SP͒ at high temperatures on the basis of the following properties: ͑a͒ their anhysteretic magnetization curves are well described in terms of Langevin functions; ͑b͒ in some cases, the classical ''superparamagnetic'' scaling law of the reduced magnetization M /M S with M S (H/T) has been approximately observed; 25,26 at low temperatures, deviations from the M S (H/T) law in samples containing chemically homogeneous particles are usually ascribed to single-particle blocking. A number of experimental papers have been published in the last decade based upon the assumption that the particle moments are completely noninteracting.…”

Microstructures and magnetic properties of Co–Cu nanoparticles prepared by arc-discharge

“…Recently, interest has increased on single domain particles immersed in a nonmagnetic metallic matrix. The granular materials have drawn attention due to a large giant magnetoresistance (GMR) mainly resulting from the spindependent scattering of conduction electrons at the interfaces between magnetic and nonmagnetic phases as well as within the magnetic particles [1][2][3]. The GMR amplitudes are strongly affected by the preparation technique even without changing the composition [4,5].…”

Temperature dependence of the magnetic and transport properties of Co15Cu85 magnetic granular alloys

“…Very recently, rapid quenching ͑melt-spinning͒ has been shown to be a suitable method for preparing bulk GMR CoCu granular alloys. [13][14][15] One of the important aspects of the GMR effect is its temperature dependence. A careful study of the temperature dependence of GMR and related magnetic properties is not only important in underlying its physical origin, but also beneficial to its practical applications.…”