Change in Magnetic Anisotropy at the Surface and in the Bulk of FINEMET Induced by Swift Heavy Ion Irradiation

Abstract

57Fe transmission and conversion electron Mössbauer spectroscopy as well as XRD were used to study the effect of swift heavy ion irradiation on stress-annealed FINEMET samples with a composition of Fe73.5Si13.5Nb3B9Cu1. The XRD of the samples indicated changes neither in the crystal structure nor in the texture of irradiated ribbons as compared to those of non-irradiated ones. However, changes in the magnetic anisotropy both in the bulk as well as at the surface of the FINEMET alloy ribbons irradiated by 160 MeV 132Xe ions with a fluence of 1013 ion cm−2 were revealed via the decrease in relative areas of the second and fifth lines of the magnetic sextets in the corresponding Mössbauer spectra. The irradiation-induced change in the magnetic anisotropy in the bulk was found to be similar or somewhat higher than that at the surface. The results are discussed in terms of the defects produced by irradiation and corresponding changes in the orientation of spins depending on the direction of the stress generated around these defects.

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

“…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].…”

Mössbauer Spectroscopy with a High Velocity Resolution in the Studies of Nanomaterials

“…These alloys, called “FINEMET”, were developed in 1988 [ 98 ] and are interesting by now for investigation using Mössbauer spectroscopy as one of the most powerful techniques. Variations in the soft magnetic properties of FINEMET alloys can be achieved by inducing a variation in transversal magnetic anisotropy by stress annealing under different tensile stresses or under different transversal magnetic fields as well as by defects formation using irradiation with swift heavy ions (see, e.g., [ 99 , 100 ] and references therein). Therefore, the study of the iron local microenvironments in FINEMET alloys in relation to their magnetic properties, in particular, to their magnetic anisotropy and permeability, is of interest.…”

“…The Mössbauer spectra were measured in 4096 channels and converted into 2048-channel spectra. The spectra were fitted by the model described in detail in [ 100 ]. The differential spectra are shown on the bottom.…”