2018-Sustainable Industrial Processing Summit
SIPS2018
Volume 6. New and Advanced Materials and Technologies
| Editors: | F. Kongoli, F. Marquis, P. Chen, T. Prikhna, N. Chikhradze |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2018 |
| Pages: | 392 pages |
| ISBN: | 978-1-987820-92-8 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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Magnetic Hardening of Fe-Pt and Fe-Pt- M (M=B, Si) Microwires
Valentina Zhukoa1; Mihail Ipatov1; Alexandr Aronin2; Galina Abrosimova2; Arcady Zhukov1;1DEPT. PHYS. MATER., UPV/EHU, San Sebastian, Spain; 2INSTITUTE OF SOLID STATE PHYSICS, RUSSIAN ACADEMY OF SCIENCE, Chernogolovka, Russian Federation;
Type of Paper: Regular
Id Paper: 329
Topic: 43
Abstract:
Rapid quenching from melt has been successfully used during more than 60 years for quick preparation of amorphous, nanocrystalline, or metastable crystalline materials with planar (ribbons) or cylindrical (wires) geometry. Most attention has been paid to preparation and studies of amorphous and nanocrystalline rapidly quenched materials exhibiting soft magnetic properties [1]. However, if the quenching rate achieved during the rapidly quenching process is not sufficiently high or if the phase diagram of the alloy is not appropriate for preparation of amorphous materials, a metastable crystalline material (i.e. supersaturated solid solutions, nanocrystalline, microcrystalline or granular alloys) can be prepared [1].
It is worth mentioning that even crystalline magnetic wires present a number of interesting and unusual magnetic properties suitable for various applications: propagation of single domain wall along the magnetic wire and giant magnetoimpedance effect (GMI) [1]. In fact, rapid solidification and subsequent processing is a well-established route to the formation of hard magnets[1]. Additionally, glass-coating can enhance mechanical properties of magnetic microwires. Therefore, few attempts have been made to enhance the coercivity on glass-coated microwires [1].
The principal limitation for the preparation of hard magnetic glass-coated microwires containing rare-earth metals using the Taylor-Ulitovsky method is related to the chemical interaction with the glass during the rapid quenching from the melt. This is the limiting factor for rare-earth containing materials. Therefore, recently we paid attention to FePt alloys for magnetic microwires preparation [2]. FePt magnetically hard alloys have attracted great attention because of their excellent magnetic and mechanical properties [2]. Thus, Fe-Pt alloys are quite ductile and chemically inert. Elevated coercivity of FePt alloys is usually attributed to high magnetocrystalline anisotropy of the L10 FePt phase. Moreover, FePt alloys usually present relatively high Curie temperature (T<sub>c</sub> = 750 K) and spontaneous magnetization of about 1.43 T. Consequently we have prepared Fe-Pt and Fe-Pt- M (M=B, Si) microwires using Taylor-Ulitovsky technique and studied their magnetic properties. Magnetic properties depend considerably on the metallic core composition and annealing conditions. As-prepared microwires present either amorphous or mixture of amorphous and nanocrystalline phases with a presence of BCC FePt, FCC PtFe and small amount of tetragonal FePt phase. After annealing at 500 <sup>o</sup>C Fe<sub>50</sub>Pt<sub>40</sub>Si<sub>10</sub> microwires we observed a remarkable magnetic hardening related to crystallization of as-prepared amorphous Fe<sub>50</sub>Pt<sub>40</sub>Si<sub>10</sub> microwires. Coercivity increasing from 5 Oe up to 500 Oe is attributed to the crystallization of amorphous Fe<sub>50</sub>Pt<sub>40</sub>Si<sub>10</sub> microwires. Annealed Fe<sub>50</sub>Pt<sub>50 </sub>sample present coercivity up to 800 Oe at 5K, but the magnetization of FePt is low and rapidly decreases with temperature. We discussed peculiarity of Fe<sub>50</sub>Pt<sub>50</sub> microwires considering the influence of internal stresses on magnetic ordering of Fe-atoms.