Spin-dependent transport in granular films with mixed length-scale magnetic coherence

• Published in: Journal of magnetism and magnetic materials Vol. 262; no. 1; pp. 52 - 55
• Main Authors: Vavassori, P, Angeli, E, Bisero, D, Spizzo, F, Ronconi, F
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 01.05.2003; Elsevier Science
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Diamagnetism, paramagnetism and superparamagnetism; Exact sciences and technology; Fine-particle systems; Giant magnetoresistance; Granular films; Magnetic properties and materials; Magneto-optical properties; Magnetotransport phenomena, materials for magnetotransport; Metals and alloys; Physics; Small particles and nanoscale materials; Studies of specific magnetic materials; Superparamagnetism; 75.47.−m; Magneto-optical properties; 75.50.Tt; 72.10.−d; Giant magnetoresistance; Superparamagnetism; 75.47.De; Granular films; Magnetization; Magnetic ordering; Ferromagnetic materials; Iron alloys; Experimental study; Binary alloys; Coherence length; Phenomenological model; Spin diffusion; Granular materials; Copper alloys; 72.10.-d Granular films; 75.47.-m; Microstructure; Reorientation; Silver alloys; Cobalt alloys; Diffusion length; Transition element alloys
• ISSN: 0304-8853
• DOI: 10.1016/S0304-8853(03)00017-9

We investigated the magnetoresistance effect in presence of mixed length-scale magnetic coherence in systems displaying coexistence of ferromagnetic- and superparamagnetic-like behaviors. In spite of their different microstructure, all the samples investigated show magnetoresistance curves vs. sample magnetization with a characteristic feature: the magnetoresistance remains unchanged (viz., equal to its value for M=0) over a wide range of magnetization values. The results are interpreted considering the interplay between the different magnetic ordering scales probed by the spin-dependent scattering and the magnetization reorientation processes and the presence in the films of magnetic coherence at different length-scales. From the comparison of the results with a phenomenological model, developed for dealing with local variations of magnetic ordering, we determined the field evolution of the ratio between the characteristic length-scale for magnetic coherence and spin diffusion length in the different samples.