Abstract
Thin film libraries of Fe-Co-V were fabricated by combinatorial sputtering to study magnetic and structural properties over wide ranges of composition and thickness by high-throughput methods: synchrotron X-ray diffraction, magnetometry, composition, and thickness were measured across the Fe-Co-V libraries. In-plane magnetic hysteresis loops were shown to have a coercive field of 23.9 kA m–1 (300 G) and magnetization of 1000 kA m–1. The out-of-plane direction revealed enhanced coercive fields of 207 kA m–1 (2.6 kG) which was attributed to the shape anisotropy of column grains observed with electron microscopy. Angular dependence of the switching field showed that the magnetization reversal mechanism is governed by 180° domain wall pinning. In the thickness-dependent combinatorial study, co-sputtered composition spreads had a thickness ranging from 50 to 500 nm and (Fe70Co30)100-xVx compositions of x = 2–80. Comparison of high-throughput magneto-optical Kerr effect and traditional vibrating sample magnetometer measurements show agreement of trends in coercive fields across large composition and thickness regions.
Highlights
The same researchers proposed that a pinning site at the B2 anti-phase boundaries (APBs) was responsible for the increase in coercive field observed without providing quantitative support
For our second aim (Section 3), we compared the in-plane coercive field measured by HiTp magneto-optical Kerr effect (MOKE) and regular vibrating sample magnetometer (VSM) measurements across large film thickness and composition ranges of the Fe70Co30-V sub-system
This thickness dependence study was performed to qualitatively understand the effects of using the combinatorial thin film method. This is important because magnetic films are known to exhibit dramatic changes in properties versus thin film thickness [15, 16], and the knowledge discovered with the combinatorial thin film method should be applied to processing bulk permanent magnets
Summary
Modern society relies on permanent magnets that are common in motors, generators, speakers, and actuators. We have studied alloys of Fe and Co with refractory metals including W [3], Mo [4], Nb [5], and V (this work) as part of our search for rare-earth-free permanent magnets using the combinatorial methodology. These refractory metal additions are stable at a temperature of 200°C, as required for traction motors. A second alloy called Vicalloy II requires considerable cold-working of over 90% and increased V content of 12 to 16 atomic percent (at%) for a maximum energy product about three times larger than Vicalloy I [12]. The same researchers proposed that a pinning site at the B2 anti-phase boundaries (APBs) was responsible for the increase in coercive field observed without providing quantitative support
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