Magnetic nanogranular materials, viz. systems made of nanosized magnetic (M) particles dispersed in a non magnetic (NM) matrix, have recently attracted a lot of attention thanks to their peculiar electronic conductivity. Indeed, together with M/NM multilayers, they belong to a wide class of materials that, thanks to the electron spin-filtering effect originated by the spin asymmetry typical of the transition metals conduction band, show an enhanced magnetoresistive effect, the so called giant magnetoresistance (GMR). GMR intensity and sensitivity to the external field is deeply connected to their magnetic and structural properties, and in this paper we address the latter topic by focusing on a novel type of nanogranular materials [1]. More in detail, we concentrate on samples produced combining the typical multilayer stacking with the presence of very thin M layers. Actually, below a critical thickness a layer fragmentation process is induced and a granular arrangement of magnetic species is obtained. Moreover, thanks to the inner vertical periodicity of the samples, structural techniques such as X-Ray specular reflectivity and grazing incidence small angle X-Ray scattering can be used to probe the vertical arrangement of nanograins and the self- and cross-correlation of M/NM interfaces. In addition, using the same data some details concerning the universality class the growth process belongs to can be extracted [2]. In this paper we present Co/Cu fragmented multilayers, and we follow their structural evolution as the thickness of the Co layers is reduced, viz. changing M particles average size. Due to the small difference between Co and Cu electronic density, the measurements were performed in anomalous conditions, i.e. tuning X-Ray energy in order to enhance the otherwise poor optical contrast. The structural findings deduced from this analysis will be compared with the magnetic and magnetoresistive characterization of the samples. [1] G. Turilli, L. Pareti, and L. Castaldi, Superlattices and microstructures 25, 591 (1999). F. Casoli et al., J. Magn. Magn. Mat. 262/1, 69 (2003). [2] R. Paniago et al., Phys. Rev. B 56(20) 13442 (1997).

X-Ray structural investigation of Co/Cu granular multilayers with GMR

SPIZZO, Federico;
2007

Abstract

Magnetic nanogranular materials, viz. systems made of nanosized magnetic (M) particles dispersed in a non magnetic (NM) matrix, have recently attracted a lot of attention thanks to their peculiar electronic conductivity. Indeed, together with M/NM multilayers, they belong to a wide class of materials that, thanks to the electron spin-filtering effect originated by the spin asymmetry typical of the transition metals conduction band, show an enhanced magnetoresistive effect, the so called giant magnetoresistance (GMR). GMR intensity and sensitivity to the external field is deeply connected to their magnetic and structural properties, and in this paper we address the latter topic by focusing on a novel type of nanogranular materials [1]. More in detail, we concentrate on samples produced combining the typical multilayer stacking with the presence of very thin M layers. Actually, below a critical thickness a layer fragmentation process is induced and a granular arrangement of magnetic species is obtained. Moreover, thanks to the inner vertical periodicity of the samples, structural techniques such as X-Ray specular reflectivity and grazing incidence small angle X-Ray scattering can be used to probe the vertical arrangement of nanograins and the self- and cross-correlation of M/NM interfaces. In addition, using the same data some details concerning the universality class the growth process belongs to can be extracted [2]. In this paper we present Co/Cu fragmented multilayers, and we follow their structural evolution as the thickness of the Co layers is reduced, viz. changing M particles average size. Due to the small difference between Co and Cu electronic density, the measurements were performed in anomalous conditions, i.e. tuning X-Ray energy in order to enhance the otherwise poor optical contrast. The structural findings deduced from this analysis will be compared with the magnetic and magnetoresistive characterization of the samples. [1] G. Turilli, L. Pareti, and L. Castaldi, Superlattices and microstructures 25, 591 (1999). F. Casoli et al., J. Magn. Magn. Mat. 262/1, 69 (2003). [2] R. Paniago et al., Phys. Rev. B 56(20) 13442 (1997).
2007
giant magnetoresistance; grazing incidence small angle x-ray scattering
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11392/1392716
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