Ferromagnetic resonance study of iron implanted PET foils

Abstract

Polyethylene terephthalate (PET) foils were implanted with 40 keV Fe+ ions to doses of (0.15–1.50) × 1017 ions/cm2 at ion current density of 4 µA/cm2. The iron‐implanted PET composites were investigated using ferromagnetic resonance (FMR) technique supplemented by transmission electron microscopy (TEM), atomic force microscopy (AFM) and DC resistance measurements. TEM studies revealed formation of iron nanoparticles with size in the range of 5–100 nm depending on the implantation dose. AFM images showed depending on the implantation dose either small bumps or worm‐like structures on the polymer surface that corresponded to the inclusions towered above the surface. The results of AFM studies were found to be in good agreement with the TEM measurements. FMR signal was observed for the foils implanted with the dose higher than 0.15 × 1017 ions/cm2. The effective magnetization of the metal‐polymer composite was extracted from the angular dependencies of FMR resonance field. The percolation transition at the implantation dose of 1.0 × 1017 ions/cm2 was observed in the dose dependencies of the FMR absorption intensity and the effective magnetisation. The minimum in DC resistance found at the same dose indicates that a charge carrier mediated (exchange) interaction rather than the dipolar one is underlying mechanism for the percolation transition. Formation of a carbonized layer in the heavily implanted area of the polymer is supposed to be responsible for the exchange coupling of the magnetic granules. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Magnetoresistive Effect in PET Films with Iron Nanoparticles Synthesized by Ion Implantation

“…It was shown in our earlier studies that the high-fluence implantation of iron into PET causes the nucleation of metal NPs in the near-surface layer [10]. The similar effect was also found for the case of Co + and Fe + ion implantation into polyimide [9,13].…”

“…The relative resistance is found to be a monotonous decreasing function of the external magnetic field. Though the TEM data did not show the formation of continuous iron layer for this fluence yet [10], spatial density of the iron NPs is high enough to provide effective percolation conductivity and magnetic coupling. The observed dependence is similar to that assigned in some cases to ferromagnetic metals [23] and in some cases to granular ferromagnetic films.…”

“…(1c). The analysis of the electron diffraction patterns showed that there were α-phase metallic Fe with the traces of non-magnetic iron oxides (mainly, and following saturation [10,11]. A so-called percolation transition in electrical and magnetic properties was suggested due to the formation of quasi-continuous granular iron layer in which close-located but non-overlapping Fe NPs or grains are situated in the heavily carbonized polymer.…”

“…In our earlier publications [10,11] we showed the results on the study of magnetic resonance phenomena and static magnetic properties of Fe-implanted PET. In this paper, we present the data of temperature dependence of conductance and magnetoresistive measurements and discuss magnetotransport properties of the composite Fe-PET layers.…”

“…On the one hand, the mechanisms of charge carrier transport can evolve from variable range hopping (VRH) or intercluster tunnelling for moderate metal concentration towards percolation conductance under the conditions of IMT [8]. On the other hand, an increase in the concentration of magnetic impurity in a nonmagnetic dielectric matrix leads to magnetic percolation transition from the diamagnetic to *Address correspondence to this author at the University of Gothenburg, 42196 Gothenburg, Sweden; Tel: +46 31 7723435; Fax: +46 31 7723496; E-mail: popok@physics.gu.se ferromagnetic state through the superparamagnetism of magnetic NPs [9][10][11]. Moreover, granular condensed media with magnetic ordering can demonstrate a wide spectrum of different magnetic micro-or nano-structures.…”