Swift heavy ion irradiation-induced amorphous iron and Fe–Si oxide phases in metallic 57Fe layer vacuum deposited on surface of SiO2/Si

Abstract

Abstract57Fe conversion electron Mössbauer (CEM) spectroscopy, SEM and magnetization measurements were used to study the effect of swift heavy ion irradiation on metallic 57Fe (10 nm) thin layer vacuum deposited onto SiO2/Si. About 85% of the total iron content of the surface layer detected by CEM was present as metallic, crystalline alpha iron before the irradiation, while upon irradiation with 160 MeV Xe ions, with a fluence of 5 × 1013 ion cm−2, ~ 21% was converted to amorphous iron and ~ 47% to silicon-containing iron oxide phases. The presence of pure iron in the amorphous state was evidenced by CEM in agreement with magnetization measurements. Temperature dependence of CEM measurements and the FC/ZFC curves of the irradiated deposit indicated superparamagnetic nature of the iron-silicon-oxide phases. The results are discussed in terms of the thermal spike model for the formation of the amorphous iron phase that can be essential for the formation of silicon-iron-oxides. Graphical abstract

Change in Superparamagnetic State Induced by Swift Heavy Ion Irradiation in Nano-Maghemite

“…In the case of 155 MeV Xe ion irradiation with the higher fluence of 1 × 10 14 ion cm −2 , an even larger amount, 31 × 10 18 vacancies, were created in the nano-maghemite, which could induce an even stronger effect, creating a much larger amount of irradiation-induced superparamagnetic region than in the case of the lower fluence irradiation. The results we obtained for the fluence threshold were consistent with those reported for different oxides [36,43,49,50,68,69,73,74] taking into account the difference in the irradiation parameters. The electron stopping power in our case far exceeded the 6 keV nm −1 threshold for dislocation formation estab-lished by Khara et al [39], who developed a computer model to estimate dislocation formations created by swift heavy ion irradiation, which strongly confirmed that we had a suitable amount of dislocations forming new grain boundaries resulting in increased amounts of superparamagnetic regions with fluence in nano-maghemite upon the irradiation.…”

“…The observed changes due to irradiation could be related to the accelerated diffusion of defects and ions via the molten tracks and ion beam mixing, similarly as reported in other works [43,68,69]. This theory also satisfactorily explained the results [49,50] obtained on other systems irradiated under the same irradiation conditions as the current one.…”

“…Swift heavy ion irradiation of nano-maghemite was carried out with 132 Xe 26+ ions of 160 MeV energy with a fluence of 5 × 10 13 ion cm −2 and of 155 MeV energy with a fluence of 1 × 10 14 ion cm −2 at room temperature, at a current density of 0.01 µA cm −2 and at a pressure of about 10 −3 Pa, at the IC-100 cyclotron of the Flerov Laboratory of Nuclear Reactions, JINR, Dubna, Russian Federation between 2020 and 2021. The irradiation energies and fluences were chosen according to the values at which radiation effects have already been observed in related systems [49,50] and which were actually available at the facility. The plane of the samples was oriented perpendicular to the ion beam direction.…”

“…Mössbauer spectroscopy is a unique method to study iron-oxide nanoparticles [46][47][48], especially to monitor their superparamagnetic states. Recently, we successfully applied Mössbauer spectroscopy to observe the formation of swift heavy ion irradiation-induced amorphous iron and superparamagnetic Fe-Si oxide phases [49], as well as change in magnetic anisotropy of nanostructured FINEMET alloys [50].…”

Physical Property Variation of Ferrite Nanoparticles under Heavy Ion Irradiation

“…Swift heavy ions (SHI) are well known to modify characteristics of the materials (Kuzmann et al, 2023;Wu et al, 2023) and devices such as spintronics (Singh et al, 2016;Zhao et al, 2019), electronic (Bharathi et al, 2016; and sensing (Ramola et al, 2022). These ions have the potential to design ferrites for spintronic (Garg et al, 2023) and gas sensing applications (Bagwan et al, 2022).…”