Date of this Version
JOURNAL OF APPLIED PHYSICS 114, 013906 (2013); DOI: http://dx.doi.org/10.1063/1.4812561
Nanostructured MnyGa ribbons with varying Mn concentrations including Mn1.2Ga, Mn1.4Ga, Mn1.6Ga, and Mn1.9Ga were prepared using arc-melting and melt-spinning followed by a heat treatment. Our experimental investigation of the nanostructured ribbons shows that the material with y = 1.2, 1.4, and 1.6 prefers the tetragonal L10 structure and that with y = 1.9 prefers the D022 structure. We have found a maximum saturation magnetization of 621 emu/cm3 in Mn1.2Ga which decreases monotonically to 300 emu/cm3 as y reaches 1.9. Although both the L10- and D022-MnyGa samples show a high Curie temperature (Tc) well above room temperature, the value of Tc decreases almost linearly from 702K for Mn1.9Ga to 551K for Mn1.2Ga. All the ribbons are metallic between 2K and 300K but the Mn1.2Ga also shows a resistance minimum near 15K. The observed magnetic properties of the MnyGa ribbons are consistent with the competing ferromagnetic coupling between Mn moments in the regular L10-MnGa lattice sites and antiferromagnetic coupling with excess Mn moments occupying Ga sites.