Formation of the magnetic fractal structure in CoSiO₂ granular nanocomposite system at percolation threshold

Abstract

Magnetic and structural properties of (Co) x (SiO 2 ) 1 À x nanocomposite systems have been investigated over a wide range of Co concentrations using small-angle neutron scattering in combination with magnetic, magneto-optic, and magnetotransport characterization. It was found that in the region of structural percolation ðx ¼ 0:46:::0:6Þ, the characteristics of magnetically correlated clusters are several times larger than the structural size of Co granules. Starting from the percolation point, the spatial distribution of magnetic nanoclusters can be described by the surface fractal model. With further growth of cobalt concentration x ! 0.67 the formation of three-dimensional (3D) magnetic domains with typical sizes of 1.5 mm was observed.ß 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1 Introduction Composite materials based on nanoparticles of magnetic metals dispersed in the nonmagnetic matrix are of great interest not only for fundamental study, but also for its possible applications. Physical properties of such composites can be diametrically opposite to the properties of original bulk materials. Composite materials have unique characteristics like giant magnetoresistance, giant tunnel magnetoresistance [1], and the giant anomalous Hall effect [2]. Moreover, the typical granular systems show featured behavior in linear and nonlinear optical and magneto-optical (MO) experiments [3,4]. Nowadays MO properties of granular alloys are studied because of possible application as magneto-active recording media and wide range MO sensors. Recently it was suggested that granular alloys could be used as MO elements in magneto-photon crystals [5]. It has been shown, that magneto-transport and, especially, MO effects are sensitive not only to characteristic dimensions, shape and topology of granules, but also to variations in their magnetic or electronic structure [6]. Analysis of the magnetic interaction of granules and the clusters they form is very important for a correct explanation of the observed properties of granular nanocomposites.

CoPt–Al2O3 Nanocomposite Films: Synthesis, Structure, and Magnetic Properties

“…Композитные наноматериалы в последние годы стали объектом многочисленных исследований, так как они обладают новыми функциональными свойствами, отличными от физических свойств их компонентов [1]. Интенсивно исследуются композитные ферромагнитные пленки, содержащие нанокластеры переходных металлов Co, Fe или Ni в диэлектрической или полупроводниковой матрице, полученные различными физическими и химическими методами [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Ранее для получения ферромагнитных нанокомпозитных пленок Fe-In 2 O 3 [12], Co-In 2 O 3 [13], Co-Al 2 O 3 [14,15], Fe-ZrO 2 [16], Co-ZrO 2 [17] были использованы термитные реакции.…”

Magnetic and Structure Properties of CoPt-In₂O₃ Nanocomposite Films

“…In recent years, composite nanomaterials have been the subject of numerous studies due to their novel functional properties that differ from the properties of their components [1]. Composite ferromagnetic films containing nanoclusters of transition-metal Co, Fe, or Ni in a dielectric or semiconductor matrix obtained by different physical and chemical methods, including the sol-gel method, spray pyrolysis, the microemulsion method, magnetron sputtering, pulsed laser deposition, ion implantation, and joint deposition have been intensively studied [2][3][4][5][6][7][8][9]. The synthesis of these nanocomposites often passes under equilibrium conditions, but lately there has been a surge in nonequilibrium processing of ferromagnetic composites using methods like pulsed laser irradiation [10], pulsed laser deposition [11], ion implantation [12,13], and the ball-milling process [14] and thermite synthesis of materials.…”

In Situ Electron Diffraction Investigation of Solid State Synthesis of Co-In2O3 Ferromagnetic Nanocomposite Thin Films

“…Composite ferromagnetic films containing nanoclusters of 3d-metals Co, Fe, and Ni in a dielectric or semiconductor matrix obtained by various physical and chemical methods, including the sol-gel method, spray pyrolysis, the microemulsion method, magnetron sputtering, pulsed laser deposition, ion implantation, and joint deposition have been intensively studied. [1][2][3][4][5][6][7][8][9] Although the synthesis of these nanocomposites often passes under equilibrium conditions, the magnetic and other physicochemical properties strongly depend on the fabrication technique used, the particle size and concentration, and the type of chemical bond between the nanoparticles and the matrix. Recently, there has been a surge in nonequilibrium processing of ferromagnetic composites using methods like pulsed laser irradiation, 10 pulsed laser deposition, 11 ion implantation, 12,13 and ball-milling.…”