Enhanced trapped field in MgB2 bulk magnets by tuning grain boundary pinning through milling. (14th April 2015)

• Record Type: Journal Article
• Authors: Sugino, Sho; Yamamoto, Akiyasu; Shimoyama, Jun-ichi; Kishio, Kohji
• Is Part Of: Superconductor science & technology. Volume 28:Number 5(2015:May)
• Publication Date: 2015-04-14
• Subjects: MgB2 -- superconducting bulk magnet -- trapped field -- grain boundaries -- flux pinning -- milling -- permanent magnet; Superconductivity -- Periodicals; Superconductors -- Periodicals; 537.623
• DOI: 10.1088/0953-2048/28/5/055016
• Languages: English
• ISSNs: 0953-2048

Abstract

Abstract: The effects of the grain size, lattice strain, and microstructure on the trapped field properties of ball-milled MgB2 bulks were studied. A decrease in the in-plane lattice parameters and transition temperature and an increase in the in-plane x-ray diffraction peak widths occurred with milling as a result of grain refinement and carbon substitution. Microstructural analysis revealed that sub-micron-size fine MgB2 grains were well connected, resulting in increased grain boundary density. The trapped field of the magnetized bulk samples exhibited a large improvement with milling and reached 3.72 T at 5 K, which is the highest among MgB2 bulks prepared using pressureless synthesis. Excess milling resulted in degradation of the trapped field because of T c reduction. The increased grain boundary density and electron scattering are considered to contribute to the high trapped field through quantitatively and qualitatively enhancing the grain boundary flux pinning.