Coercivity enhancement in Mn-Al-Cu flakes produced by surfactant-assisted milling

We herein report the achievement of exceptionally high coercivity (H-c) values: 9.92 and 5.86 kOe at 5 and 300 K, respectively, for Mn55Al43Cu2 flakes produced by surfactant-assisted milling process without employing any heat-treatment. The use of surfactants such as oleic acid and oleylamine during milling yielded high-aspect ratio flakes for the Mn-Al-Cu alloy. Structural studies confirmed the presence of tau- and beta-phases as the major constituents in the Mn-Al-Cu flakes. The observed H-c enhancement is due to the increase in anisotropy field and structural defects, which is hypothesized to originate from the domain-wall pinning as a consequence of precipitation of fine Cu-particles present at the grain boundaries. (C) 2015 AIP Publishing LLC.