Magnetic Domain Structures in Cerium-Doped Fe 80 B 20 , Fe 80 B 16 Si 2 C 2 , and Fe 78 B 13 Si 9 Glassy Ribbons
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MAGNETIC DOMAIN STRUCTURES IN CERIUM-DOPED Fe8 oB2 0 , Fe8 0B1 6Si 2 C2 , AND Fe78B13 Si 9 GLASSY RIBBONS* AND D. M. KROEGER*** S. CANRIGHT** G. **University of Tennessee, Department of Physics, Knoxville, TN 37996 ***Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 ABSTRACT The addition of cerium in parts-per-million quantities has been shown to be effective in inhibiting the annealing embrittlement of melt-spun amorphous ribbons [1]. The effects of cerium doping on magnetic domain structures are reported in this paper. Domain structures have been observed using the Bitter colloid technique on the free surfaces of asquenched ribbons, as well as on both surfaces of ribbons which have been thinned by electropolishing. In the binary and quaternary alloys, the optimum (in terms of mechanical properties) cerium content gives ribbons which are apparently free of quenched-in stresses, since they lack the commonly observed "maze domains" which are found for both undoped and excessively doped ribbons. In contrast, the ternary alloy, which shows little decrease in annealing embrittlement versus doping, is free of maze domains in the as-quenched condition, with or without doping. The effect on the former two alloys is interpreted in terms of enhanced stress-relief during the quench. INTRODUCTION Iron-based metallic glasses exhibit a combination of high magnetization and low ac losses which makes them attractive candidate materials for power-handling magnetic cores. In previous work [1,2] we have shown that the tendency of these materials to embrittle upon annealing can, in some cases, be eliminated by doping with an appropriate amount (-75 atomic ppm) of cerium. Some effects of doping with cerium on the magnetic properties and magnetic domain structure were also seen [2,3]. In this paper we report on further studies of the magnetic domain structures versus doping for melt-spun ribbons of three alloys: Fe8 oB20 (binary), Fe78B13Si 9 (ternary), and Fe8 0B1 6Si 2C2 (quaternary). EXPERIMENTAL Ribbons were made by melt-spinning in helium gas; details of alloy preparation and melt-spinning are described elsewhere [2]. Cerium concentrations in the ribbons were found to be -40% of those in the ingots, as determined by energy dispersive X-ray fluorescence analysis [2]. Concentrations reported in this paper are nominal values, i.e., ingot concentrations. Magnetic domain structures were observed using the Bitter technique [4] on samples -2 cm long. Electropolishing was done using 1.5 cm samples. The electrolyte was one-third nitric acid and two-thirds methanol; current density was -70 mA/cm 2 . Domain structures were observed for at least four thinned samples, and numerous unthinned samples, of each alloy. *Research sponsored by the Office of Energy Storage and Distribution, Electric Energy Systems Program, U.S. Department of Energy, under contract DE-ACO5-840R21400 with Martin Marietta Energy Systems, Inc.
Mat. Res. Soc. Symp. Proc. Vol. 58. , 1986 Materials Research Society
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As-quenched domain p
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