Impact of Ion Irradiation upon Structure and Magnetic Properties of NANOPERM‐Type Amorphous and Nanocrystalline Alloys

Abstract

Structural modifications and their impact upon magnetic properties are studied in amorphous and nanocrystalline NANOPERM-type57Fe75Mo8Cu1B16alloy. They are introduced by irradiation with 130 keV N+ions to the total fluencies of up to 2.5 × 1017 ions/cm2under different cooling conditions. Increased temperature during the irradiation triggers formation of nanocrystallites of bcc-Fe in those subsurface regions that are affected by bombarding ions. No crystallization occurs when good thermal contact between the irradiated sample and a sample holder is assured. Instead, structural rearrangement which favours development of magnetically active regions was determined by the local probe methods of Mössbauer spectrometry. Dipole magnetic interactions dominate in subsurface regions on that side of the ribbons which was exposed to ion irradiation. Nevertheless, structural modifications demonstrate themselves also via macroscopic magnetic parameters such as temperature dependence of magnetization, Curie temperature, and hysteresis loops. Impact of only the temperature itself to the observed effects is assessed by the help of samples that were subjected just to heat treatment, that is, without ion irradiation.

Thermomechanical processing of metallic glasses: extending the range of the glassy state

“…Under given conditions, the same steady state can be approached from both lower-and higher-energy states 119 , and the steady-state energy is higher under more intense irradiation 121 . Irradiation can lower the energy of glasses not only by structural relaxation 122 , but also by partial nanocrystallization [123][124][125] .…”

Radiation Effects in Amorphous Metallic Alloys as Revealed by Mössbauer Spectrometry: Part II. Ion Irradiation

“…They are the so-called Conversion Electron Mössbauer Spectrometry (CEMS) and Conversion X-ray Mössbauer Spectrometry (CXMS) which provide information from subsurface regions down to the depth of ~200 nm and ~5 µm, respectively. They are especially suited for investigation of surface properties [44] including ion-irradiation induced radiation damage that is usually located in near surface regions [36][37][38][39]. In this way, it is possible to acquire complex information from both the whole sample's interior and/or its surface.…”

“…In order to ensure appropriate thermal contact with the irradiation base and, thus, to warrant that the ribbons will be not overheated during ion bombardment, pieces of the ribbons were firmly attached to a cooled sample holder. Failure to follow this condition might lead to irradiation-induced enhanced thermal load with a consequent crystallization of originally amorphous ribbons [38].…”

“…It is noteworthy that studies of irradiation effects caused by low-and medium-energy ions upon classical compositions of AMAs are also reported and recently attracted the interest of several research groups [8,9,[31][32][33][34][35]. Nonetheless, Mössbauer effect studies in this field are not so abundant [36][37][38][39] and it is not surprising that they emphasise the importance of surface modifications which are unveiled by the help of the CEMS technique. Eventually, conversion X-ray Mössbauer spectrometry (CXMS), which scans deeper surface regions than the CEMS technique, is also applied [38].…”

“…Nonetheless, Mössbauer effect studies in this field are not so abundant [36][37][38][39] and it is not surprising that they emphasise the importance of surface modifications which are unveiled by the help of the CEMS technique. Eventually, conversion X-ray Mössbauer spectrometry (CXMS), which scans deeper surface regions than the CEMS technique, is also applied [38].…”