Properties of Zirconium Oxide and Cobalt Ferrite Layered Nanocomposite

Abstract

CoFe 2 O 4 nanoparticles with 3-30 nm in diameter were synthesized by sol-gel method. The particles were spread as a solid discontinuous layer over planar silicon and TiN substrates by spin coating and covered by 15 nm thick ZrO 2 films by atomic layer deposition. Crystal structures distinctively characteristic of CoFe 2 O 4 and ZrO 2 constituents were preserved. The nanocomposite CoFe 2 O 4 -ZrO 2 layers demonstrated dielectric polarization, saturative magnetization, and implications of resistive switching behavior. Behavior most clearly attributed to memory materials was observed in the field admittance characteristic with two distinct states in susceptibility of the nanocomposite. There is permanent and growing interest in complex compound materials for a variety of applications in which the components tailor their best structural, mechanical, optical or electronic properties making the material versatile for the planned applications. Metal oxide based layered systems can demonstrate a variety of resistive switching, ferroelectric, ferromagnetic and other properties useful in prospective devices.1 Cobalt-iron-oxygen ternary system has been of considerable interest, driven perhaps by the necessity of use it as a constituent compound in more complex structures exploited in solid oxide fuel cells. 2 Cobalt ferrite has been studied 3 as an attractive magnetic material suited to magneto-optical recording, integrated optics, or waveguides, due to its potential combination of semiconducting and magnetic properties including high coercivity, anisotropy, and magnetostriction.CoFe Regarding other 3D structures based on cobalt ferrite, Co x Fe 3−x O 4 magnetic thin films have been grown on the pore walls of alumina membranes by atomic layer deposition. 17 Cobalt ferrite in thin film form has also been prepared by spray pyrolysis using cobalt and iron nitrate precursors.18 Magnetization-field or Kerr loops with certain coercive force has earlier been recorded in CoFe 2 O 4 particles [3][4][5][6]8,10,14,16 and thin films, 18 in most cases at room temperature. Ferromagnetic CoFe 2 O 4 particles have been added to YBa 2 Cu 3 O 7-δ thin films to enhance flux pinning in potentially superconducting materials which, however, led to the formation of Y(Fe,Co)O 3 , leaving the host material yttrium-deficient. 19 On the other hand, dilute Fe and Co codoping into ZrO 2 has resulted in ferromagnetic behavior at room temperature for annealing temperatures above 900• C, suggesting that partial formation of secondary phases, such as cobalt ferrite, promoted ferromagnetism. 20 Very small CoFe 2 O 4 particles with diameter 4-6 nm alone have also demonstrated magnetization decreasing toward higher temperatures and have thus been described as superparamagnetic. 6,9 Coercive field decreased substantially with increasing temperature, although saturative magnetization could be achieved at room temperature as well. CoFe 2 O 4 particles embedded in SiO 2 /ZrO 2 host matrix have been studied and characterized as magneto-optical isolators and desc...

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Observation of CCNR-type electrical switching in Zn0.3Mn0.7+xSixFe2−2xO4 spinel ferrite series

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